I've added Selene, Supplementaries and Skinned Lanterns along with the mods I'd been using beforehand. Everything was fine, then maybe 2 or 3 days later it suddenly started hard crashing with this same error. As of the error Forge and Java were both up to date as far as I could see. I tried deleting the entities file altogether and reloading, tried an earlier backup, rolled back the java version installed, fresh install of the server, a computer restart between each step and eventually had to remove the mods 1 by 1 to figure out which was causing it. This is the last crash report before I got it running by removing the mods.

`---- Minecraft Crash Report ----
// I let you down. Sorry :(

Time: 2021-10-27, 10:04 p.m.
Description: Exception ticking world

java.lang.RuntimeException: Attempted to load class net/minecraft/client/multiplayer/ClientLevel for invalid dist DEDICATED_SERVER
at net.minecraftforge.fml.loading.RuntimeDistCleaner.processClassWithFlags(RuntimeDistCleaner.java:71) ~[fmlloader-1.17.1-37.0.103.jar%2322!:1.0] {}
at cpw.mods.modlauncher.LaunchPluginHandler.offerClassNodeToPlugins(LaunchPluginHandler.java:88) ~[modlauncher-9.0.7.jar%235!:?] {}
at cpw.mods.modlauncher.ClassTransformer.transform(ClassTransformer.java:120) ~[modlauncher-9.0.7.jar%235!:?] {}
at cpw.mods.modlauncher.TransformingClassLoader.maybeTransformClassBytes(TransformingClassLoader.java:50) ~[modlauncher-9.0.7.jar%235!:?] {}
at cpw.mods.cl.ModuleClassLoader.readerToClass(ModuleClassLoader.java:110) ~[securejarhandler-0.9.54.jar:?] {}
at cpw.mods.cl.ModuleClassLoader.lambda$findClass$16(ModuleClassLoader.java:213) ~[securejarhandler-0.9.54.jar:?] {}
at cpw.mods.cl.ModuleClassLoader.loadFromModule(ModuleClassLoader.java:223) ~[securejarhandler-0.9.54.jar:?] {}
at cpw.mods.cl.ModuleClassLoader.findClass(ModuleClassLoader.java:213) ~[securejarhandler-0.9.54.jar:?] {}
at cpw.mods.cl.ModuleClassLoader.loadClass(ModuleClassLoader.java:130) ~[securejarhandler-0.9.54.jar:?] {}
at java.lang.ClassLoader.loadClass(ClassLoader.java:520) ~[?:?] {}
at net.minecraft.world.level.saveddata.maps.MapItemSavedData.handler$zzc000$getUpdatePacket(SourceFile:814) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:mixin,re:classloading,pl:mixin:APP:selene.mixins.json:MapDataMixin,pl:mixin:A}
at net.minecraft.world.level.saveddata.maps.MapItemSavedData.m_164796_(SourceFile:421) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:mixin,re:classloading,pl:mixin:APP:selene.mixins.json:MapDataMixin,pl:mixin:A}
at net.minecraft.server.level.ServerEntity.m_8533_(ServerEntity.java:89) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading}
at net.minecraft.server.level.ChunkMap.m_140421_(ChunkMap.java:994) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading,pl:accesstransformer:B}
at net.minecraft.server.level.ServerChunkCache.m_8490_(ServerChunkCache.java:364) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading,pl:accesstransformer:B}
at net.minecraft.server.level.ServerChunkCache.m_142483_(ServerChunkCache.java:311) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading,pl:accesstransformer:B}
at net.minecraft.server.level.ServerLevel.m_8793_(ServerLevel.java:347) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading,pl:accesstransformer:B,re:mixin,pl:accesstransformer:B}
at net.minecraft.server.MinecraftServer.m_5703_(MinecraftServer.java:882) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading,pl:accesstransformer:B,re:mixin,pl:accesstransformer:B}
at net.minecraft.server.dedicated.DedicatedServer.m_5703_(DedicatedServer.java:334) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading,pl:accesstransformer:B}
at net.minecraft.server.MinecraftServer.m_5705_(MinecraftServer.java:818) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading,pl:accesstransformer:B,re:mixin,pl:accesstransformer:B}
at net.minecraft.server.MinecraftServer.m_130011_(MinecraftServer.java:683) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading,pl:accesstransformer:B,re:mixin,pl:accesstransformer:B}
at net.minecraft.server.MinecraftServer.m_177918_(MinecraftServer.java:258) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading,pl:accesstransformer:B,re:mixin,pl:accesstransformer:B}
at java.lang.Thread.run(Thread.java:833) [?:?] {}

A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Thread: Server thread
Stacktrace:
at net.minecraftforge.fml.loading.RuntimeDistCleaner.processClassWithFlags(RuntimeDistCleaner.java:71) ~[fmlloader-1.17.1-37.0.103.jar%2322!:1.0] {}
at cpw.mods.modlauncher.LaunchPluginHandler.offerClassNodeToPlugins(LaunchPluginHandler.java:88) ~[modlauncher-9.0.7.jar%235!:?] {}
at cpw.mods.modlauncher.ClassTransformer.transform(ClassTransformer.java:120) ~[modlauncher-9.0.7.jar%235!:?] {}
at cpw.mods.modlauncher.TransformingClassLoader.maybeTransformClassBytes(TransformingClassLoader.java:50) ~[modlauncher-9.0.7.jar%235!:?] {}
at cpw.mods.cl.ModuleClassLoader.readerToClass(ModuleClassLoader.java:110) ~[securejarhandler-0.9.54.jar:?] {}
at cpw.mods.cl.ModuleClassLoader.lambda$findClass$16(ModuleClassLoader.java:213) ~[securejarhandler-0.9.54.jar:?] {}
at cpw.mods.cl.ModuleClassLoader.loadFromModule(ModuleClassLoader.java:223) ~[securejarhandler-0.9.54.jar:?] {}
at cpw.mods.cl.ModuleClassLoader.findClass(ModuleClassLoader.java:213) ~[securejarhandler-0.9.54.jar:?] {}
at cpw.mods.cl.ModuleClassLoader.loadClass(ModuleClassLoader.java:130) ~[securejarhandler-0.9.54.jar:?] {}
at java.lang.ClassLoader.loadClass(ClassLoader.java:520) ~[?:?] {}
at net.minecraft.world.level.saveddata.maps.MapItemSavedData.handler$zzc000$getUpdatePacket(SourceFile:814) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:mixin,re:classloading,pl:mixin:APP:selene.mixins.json:MapDataMixin,pl:mixin:A}
at net.minecraft.world.level.saveddata.maps.MapItemSavedData.m_164796_(SourceFile:421) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:mixin,re:classloading,pl:mixin:APP:selene.mixins.json:MapDataMixin,pl:mixin:A}
at net.minecraft.server.level.ServerEntity.m_8533_(ServerEntity.java:89) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading}
at net.minecraft.server.level.ChunkMap.m_140421_(ChunkMap.java:994) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading,pl:accesstransformer:B}
at net.minecraft.server.level.ServerChunkCache.m_8490_(ServerChunkCache.java:364) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading,pl:accesstransformer:B}
at net.minecraft.server.level.ServerChunkCache.m_142483_(ServerChunkCache.java:311) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading,pl:accesstransformer:B}
at net.minecraft.server.level.ServerLevel.m_8793_(ServerLevel.java:347) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading,pl:accesstransformer:B,re:mixin,pl:accesstransformer:B}
-- Affected level --
Details:
All players: 1 total; [ServerPlayer['B10Reaper'/669, l='ServerLevel[Brimbleton]', x=-1591.75, y=103.35, z=-1138.50]]
Chunk stats: 3862
Level dimension: minecraft:overworld
Level spawn location: World: (-1276,71,-936), Section: (at 4,7,8 in -80,4,-59; chunk contains blocks -1280,0,-944 to -1265,255,-929), Region: (-3,-2; contains chunks -96,-64 to -65,-33, blocks -1536,0,-1024 to -1025,255,-513)
Level time: 11335902 game time, 2657979 day time
Level name:
Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: true
Level weather: Rain time: 41154 (now: false), thunder time: 57631 (now: false)
Known server brands: forge
Level was modded: true
Level storage version: 0x04ABD - Anvil
Stacktrace:
at net.minecraft.server.MinecraftServer.m_5703_(MinecraftServer.java:882) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading,pl:accesstransformer:B,re:mixin,pl:accesstransformer:B}
at net.minecraft.server.dedicated.DedicatedServer.m_5703_(DedicatedServer.java:334) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading,pl:accesstransformer:B}
at net.minecraft.server.MinecraftServer.m_5705_(MinecraftServer.java:818) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading,pl:accesstransformer:B,re:mixin,pl:accesstransformer:B}
at net.minecraft.server.MinecraftServer.m_130011_(MinecraftServer.java:683) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading,pl:accesstransformer:B,re:mixin,pl:accesstransformer:B}
at net.minecraft.server.MinecraftServer.m_177918_(MinecraftServer.java:258) ~[server-1.17.1-20210706.113038-srg.jar%2352!:?] {re:classloading,pl:accesstransformer:B,re:mixin,pl:accesstransformer:B}
at java.lang.Thread.run(Thread.java:833) [?:?] {}

-- System Details --
Details:
Minecraft Version: 1.17.1
Minecraft Version ID: 1.17.1
Operating System: Windows 10 (amd64) version 10.0
Java Version: 17, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode, sharing), Oracle Corporation
Memory: 9177554072 bytes (8752 MiB) / 10737418240 bytes (10240 MiB) up to 16106127360 bytes (15360 MiB)
CPUs: 8
Processor Vendor: GenuineIntel
Processor Name: Intel(R) Core(TM) i7 CPU 920 @ 2.67GHz
Identifier: Intel64 Family 6 Model 26 Stepping 5
Microarchitecture: Nehalem (Server)
Frequency (GHz): 2.67
Number of physical packages: 1
Number of physical CPUs: 4
Number of logical CPUs: 8
Graphics card #0 name: NVIDIA GeForce GTX 1050 Ti
Graphics card #0 vendor: NVIDIA (0x10de)
Graphics card #0 VRAM (MB): 4095.00
Graphics card #0 deviceId: 0x1c82
Graphics card #0 versionInfo: DriverVersion=30.0.14.9649
Memory slot #0 capacity (MB): 4096.00
Memory slot #0 clockSpeed (GHz): 1.07
Memory slot #0 type: Other
Memory slot #1 capacity (MB): 4096.00
Memory slot #1 clockSpeed (GHz): 1.07
Memory slot #1 type: Other
Memory slot #2 capacity (MB): 4096.00
Memory slot #2 clockSpeed (GHz): 1.07
Memory slot #2 type: Other
Memory slot #3 capacity (MB): 4096.00
Memory slot #3 clockSpeed (GHz): 1.07
Memory slot #3 type: Other
Memory slot #4 capacity (MB): 2048.00
Memory slot #4 clockSpeed (GHz): 1.07
Memory slot #4 type: Other
Memory slot #5 capacity (MB): 2048.00
Memory slot #5 clockSpeed (GHz): 1.07
Memory slot #5 type: Other
Virtual memory max (MB): 81911.11
Virtual memory used (MB): 42563.62
Swap memory total (MB): 61440.00
Swap memory used (MB): 156.04
JVM Flags: 2 total; -Xmx15G -Xms10G
Player Count: 1 / 5; [ServerPlayer['(Redacted), l='ServerLevel[Redacted]', x=-1591.75, y=103.35, z=-1138.50]]
Data Packs: vanilla, mod:configured (incompatible), mod:thevanillaexperience, mod:buildersaddition (incompatible), mod:snowundertrees, mod:worldedit (incompatible), mod:biomesoplenty, mod:cfm, mod:catalogue (incompatible), mod:extendedcreativeinventory, mod:cloth_config (incompatible), mod:forge, mod:bambooeverything (incompatible), mod:goldenhopper, mod:collective, mod:configurableextramobdrops, mod:craftingautomat (incompatible), mod:the_wild_update, mod:dynview (incompatible), mod:restored_earth, mod:absentbydesign (incompatible), mod:citadel (incompatible), mod:alexsmobs (incompatible), mod:additionallanterns, mod:skinnedlanterns (incompatible), mod:supermartijn642corelib (incompatible), mod:supplementaries (incompatible), mod:selene (incompatible), mod:mcwlights (incompatible)
Is Modded: Definitely; Server brand changed to 'forge'
Type: Dedicated Server (map_server.txt)
ModLauncher: 9.0.7+91+master.8569cdf
ModLauncher launch target: forgeserver
ModLauncher naming: srg
ModLauncher services:
mixin PLUGINSERVICE
eventbus PLUGINSERVICE
object_holder_definalize PLUGINSERVICE
runtime_enum_extender PLUGINSERVICE
capability_token_subclass PLUGINSERVICE
capability_inject_definalize PLUGINSERVICE
accesstransformer PLUGINSERVICE
runtimedistcleaner PLUGINSERVICE
mixin TRANSFORMATIONSERVICE
fml TRANSFORMATIONSERVICE
FML Language Providers:
[email protected]
javafml@null
Mod List:
server-1.17.1-20210706.113038-srg.jar |Minecraft |minecraft |1.17.1 |DONE |Manifest: NOSIGNATURE
The_Wild_Update_Mod_V0.5_Minecraft_1.17.1.jar |The Wild Update 1.19 Mod |the_wild_update |0.5 |DONE |Manifest: NOSIGNATURE
BiomesOPlenty-1.17.1-14.0.0.36-universal.jar |Biomes O' Plenty |biomesoplenty |1.17.1-14.0.0.36 |DONE |Manifest: NOSIGNATURE
CraftingAutomat-MC1.17.1-1.2.2.jar |Crafting Automat |craftingautomat |1.2.2 |DONE |Manifest: NOSIGNATURE
additionallanterns-1.0.0a-mc1.17.jar |Additional Lanterns |additionallanterns |1.0.0a |DONE |Manifest: NOSIGNATURE
skinned_lanterns-1.17.1-1.3.1.jar |Skinned Lanterns |skinnedlanterns |1.17.1-1.3.1 |DONE |Manifest: NOSIGNATURE
supermartijn642corelib-1.0.12-mc1.17.jar |SuperMartijn642's Core Lib |supermartijn642corelib |1.0.12 |DONE |Manifest: NOSIGNATURE
bambooeverything-1.1.1-build.4+mc1.17.1.jar |Bamboo Everything |bambooeverything |1.1.1-build.4+mc1.17|DONE |Manifest: NOSIGNATURE
goldenhopper-1.2.4-1.17.1.jar |Golden Hopper |goldenhopper |1.2.4 |DONE |Manifest: NOSIGNATURE
1collective-1.17.1-2.64.jar |Collective |collective |2.64 |DONE |Manifest: NOSIGNATURE
configurableextramobdrops_1.17.1-1.6.jar |Configurable Extra Mob Drops |configurableextramobdrops |1.6 |DONE |Manifest: NOSIGNATURE
citadel-1.9.3-1.17.1.jar |Citadel |citadel |1.9.3 |DONE |Manifest: NOSIGNATURE
alexsmobs-1.13.1.jar |Alex's Mobs |alexsmobs |1.13.1 |DONE |Manifest: NOSIGNATURE
configured-1.2.0-1.17.1.jar |Configured |configured |1.2.0 |DONE |Manifest: NOSIGNATURE
thevanillaexperience_1.17.1-1.4.jar |The Vanilla Experience |thevanillaexperience |1.4 |DONE |Manifest: NOSIGNATURE
buildersaddition-1.17.1-20210823a.jar |Builders Crafts & Addition |buildersaddition |1.17.1-20210823a |DONE |Manifest: NOSIGNATURE
snowundertrees-1.17.1-1.1.5.jar |Snow Under Trees |snowundertrees |1.1.5 |DONE |Manifest: NOSIGNATURE
worldedit-mod-7.2.6.jar |WorldEdit |worldedit |7.2.6+4b2d1e7 |DONE |Manifest: NOSIGNATURE
cfm-7.0.0pre25-1.17.1.jar |MrCrayfish's Furniture Mod |cfm |7.0.0-pre25 |DONE |Manifest: NOSIGNATURE
catalogue-1.3.0-1.17.1.jar |Catalogue |catalogue |1.3.0 |DONE |Manifest: NOSIGNATURE
extendedcreativeinventory_1.17.1-1.6.jar |Extended Creative Inventory |extendedcreativeinventory |1.6 |DONE |Manifest: NOSIGNATURE
dynviewdist-2.2.jar |Dynamic view distance |dynview |1.8 |DONE |Manifest: NOSIGNATURE
restored_earth-1.17.1-1.1.0.jar |Restored Earth |restored_earth |1.1.0 |DONE |Manifest: NOSIGNATURE
cloth-config-5.0.38-forge.jar |Cloth Config v4 API |cloth_config |5.0.38 |DONE |Manifest: NOSIGNATURE
forge-1.17.1-37.0.103-universal.jar |Forge |forge |37.0.103 |DONE |Manifest: 22:af:21:d8:19:82:7f:93:94:fe:2b:ac:b7:e4:41:57:68:39:87:b1:a7:5c:c6:44:f9:25:74:21:14:f5:0d:90
absentbydesign-1.17.1-1.6.0.jar |Absent By Design Mod |absentbydesign |1.17.1-1.6.0 |DONE |Manifest: 1f:47:ac:b1:61:82:96:b8:47:19:16:d2:61:81:11:60:3a:06:4b:61:31:56:7d:44:31:1e:0c:6f:22:5b:4c:ed
supplementaries-1.17.1-0.18.0a.jar |Supplementaries |supplementaries |1.17.1-0.18.0 |DONE |Manifest: NOSIGNATURE
selene-1.17.1-1.9.0.jar |Selene |selene |1.17.1-1.1 |DONE |Manifest: NOSIGNATURE
mcw-lights-1.0.1-mc1.17.1.jar |Macaw's Lights and Lamps |mcwlights |1.0.1 |DONE |Manifest: NOSIGNATURE
Crash Report UUID: 963c9cc4-0643-4243-858d-7e9999fc885e
FML: 37.0
Forge: net.minecraftforge:37.0.103`

I'll fix soon. Current 1.17 release is still in alpha stage and so it might have more issues like this

is the issue resolved?