When I place the hearth for first time in world and add lava the server crash, if I log in again and remove the lava and then add it again nothing happens, it only happen the first time, so if I add another hearth to the world and add lava, the server crash.
Forge.1.18.2.Crash.Report.txt

Not sure why this is happening, as I have a check in place for this exact thing. I'm looking into it now

Happens with coal or any fuel also.

From the log, my guess would be a method calling a class that's being used by the server that's flagged for the client only.

java.lang.RuntimeException: Attempted to load class net/minecraft/client/Minecraft for invalid dist DEDICATED_SERVER at net.minecraftforge.fml.loading.RuntimeDistCleaner.processClassWithFlags(RuntimeDistCleaner.java:57) ~[fmlloader-1.18.2-40.1.80.jar%2317!/:1.0] {} at cpw.mods.modlauncher.LaunchPluginHandler.offerClassNodeToPlugins(LaunchPluginHandler.java:88) ~[modlauncher-9.1.3.jar%235!/:?] {} at cpw.mods.modlauncher.ClassTransformer.transform(ClassTransformer.java:120) ~[modlauncher-9.1.3.jar%235!/:?] {} at cpw.mods.modlauncher.TransformingClassLoader.maybeTransformClassBytes(TransformingClassLoader.java:50) ~[modlauncher-9.1.3.jar%235!/:?] {} at cpw.mods.cl.ModuleClassLoader.readerToClass(ModuleClassLoader.java:110) ~[securejarhandler-1.0.3.jar:?] {} at cpw.mods.cl.ModuleClassLoader.lambda$findClass$16(ModuleClassLoader.java:216) ~[securejarhandler-1.0.3.jar:?] {} at cpw.mods.cl.ModuleClassLoader.loadFromModule(ModuleClassLoader.java:226) ~[securejarhandler-1.0.3.jar:?] {} at cpw.mods.cl.ModuleClassLoader.findClass(ModuleClassLoader.java:216) ~[securejarhandler-1.0.3.jar:?] {} at cpw.mods.cl.ModuleClassLoader.loadClass(ModuleClassLoader.java:132) ~[securejarhandler-1.0.3.jar:?] {} at java.lang.ClassLoader.loadClass(ClassLoader.java:520) ~[?:?] {} at dev.momostudios.coldsweat.common.blockentity.HearthBlockEntity.tick(HearthBlockEntity.java:334) ~[ColdSweat-2.1.10.2.jar%23116!/:2.1.10.2] {re:classloading} at dev.momostudios.coldsweat.common.blockentity.HearthBlockEntity.tickSelf(HearthBlockEntity.java:160) ~[ColdSweat-2.1.10.2.jar%23116!/:2.1.10.2] {re:classloading} at net.minecraft.world.level.chunk.LevelChunk$BoundTickingBlockEntity.m_142224_(LevelChunk.java:673) ~[server-1.18.2-20220404.173914-srg.jar%23424!/:?] {re:classloading} at net.minecraft.world.level.chunk.LevelChunk$RebindableTickingBlockEntityWrapper.m_142224_(LevelChunk.java:766) ~[server-1.18.2-20220404.173914-srg.jar%23424!/:?] {re:classloading} at net.minecraft.world.level.Level.m_46463_(Level.java:476) ~[server-1.18.2-20220404.173914-srg.jar%23424!/:?] {re:computing_frames,pl:accesstransformer:B,re:mixin,pl:accesstransformer:B,re:classloading,pl:accesstransformer:B,pl:mixin:APP:radium.mixins.json:alloc.chunk_random.WorldMixin,pl:mixin:APP:radium.mixins.json:world.block_entity_retrieval.WorldMixin,pl:mixin:APP:radium.mixins.json:world.chunk_access.WorldMixin,pl:mixin:APP:radium.mixins.json:world.inline_block_access.WorldMixin,pl:mixin:APP:radium.mixins.json:world.inline_height.WorldMixin,pl:mixin:APP:mixins.caelum.json:MixinLevel,pl:mixin:APP:lootr.mixins.json:MixinLevel,pl:mixin:APP:biomemakeover-common.mixins.json:multipart.LevelMixin,pl:mixin:APP:sliceanddice.mixins.json:LevelMixin,pl:mixin:APP:sereneseasons.mixins.json:MixinLevel,pl:mixin:APP:beyond_earth.mixin.json:BlockSet,pl:mixin:A} at net.minecraft.server.level.ServerLevel.m_8793_(ServerLevel.java:327) ~[server-1.18.2-20220404.173914-srg.jar%23424!/:?] {re:mixin,pl:accesstransformer:B,xf:fml:forgeendertech:coremod,xf:fml:sereneseasons:temperature_transformer,re:classloading,pl:accesstransformer:B,xf:fml:forgeendertech:coremod,xf:fml:sereneseasons:temperature_transformer,pl:mixin:APP:snowrealmagic.mixins.json:ServerLevelMixin,pl:mixin:APP:supplementaries.mixins.json:ServerLevelMixin,pl:mixin:APP:wandering_trapper.mixins.json:ServerLevelMixin,pl:mixin:APP:the_bumblezone.mixins.json:world.ServerWorldMixin,pl:mixin:APP:krypton.mixins.json:server.fastchunkentityaccess.ServerWorldMixin,pl:mixin:APP:radium.mixins.json:ai.nearby_entity_tracking.ServerWorldAccessor,pl:mixin:APP:radium.mixins.json:alloc.chunk_random.ServerWorldMixin,pl:mixin:APP:radium.mixins.json:chunk.entity_class_groups.ServerWorldAccessor,pl:mixin:APP:radium.mixins.json:entity.inactive_navigations.ServerWorldMixin,pl:mixin:APP:radium.mixins.json:profiler.ServerWorldMixin,pl:mixin:APP:immersive_weathering.mixins.json:ServerLevellMixin,pl:mixin:APP:immersive_weathering.mixins.json:ServerLevelSnowMixin,pl:mixin:APP:biomemakeover-common.mixins.json:multipart.ServerLevelMixin,pl:mixin:APP:friendsandfoes-common.mixins.json:ServerWorldAccessor,pl:mixin:APP:immersiveengineering.mixins.json:coremods.ServerWorldMixin,pl:mixin:APP:byg.mixins.json:common.world.MixinServerLevel,pl:mixin:APP:betterdeserttemples.mixins.json:ServerLevelMixin,pl:mixin:APP:blueprint.mixins.json:ServerLevelMixin,pl:mixin:APP:mixins.fishofthieves.json:level.MixinServerLevel,pl:mixin:APP:create.mixins.json:accessor.ServerLevelAccessor,pl:mixin:A} at net.minecraft.server.MinecraftServer.m_5703_(MinecraftServer.java:902) ~[server-1.18.2-20220404.173914-srg.jar%23424!/:?] {re:mixin,pl:accesstransformer:B,re:computing_frames,pl:accesstransformer:B,re:classloading,pl:accesstransformer:B,pl:mixin:APP:tetrapak.mixins.json:accessor.MinecraftServerAccessor,pl:mixin:APP:mixin.excavated_variants.json:IMinecraftServerMixin,pl:mixin:APP:balm.mixins.json:MinecraftServerMixin,pl:mixin:APP:byg.mixins.json:access.MinecraftServerAccess,pl:mixin:APP:byg.mixins.json:server.MixinMinecraftServer,pl:mixin:A} at net.minecraft.server.dedicated.DedicatedServer.m_5703_(DedicatedServer.java:326) ~[server-1.18.2-20220404.173914-srg.jar%23424!/:?] {re:mixin,pl:accesstransformer:B,re:computing_frames,pl:accesstransformer:B,re:classloading,pl:accesstransformer:B,pl:mixin:APP:blueprint.mixins.json:DedicatedServerMixin,pl:mixin:A} at net.minecraft.server.MinecraftServer.m_5705_(MinecraftServer.java:842) ~[server-1.18.2-20220404.173914-srg.jar%23424!/:?] {re:mixin,pl:accesstransformer:B,re:computing_frames,pl:accesstransformer:B,re:classloading,pl:accesstransformer:B,pl:mixin:APP:tetrapak.mixins.json:accessor.MinecraftServerAccessor,pl:mixin:APP:mixin.excavated_variants.json:IMinecraftServerMixin,pl:mixin:APP:balm.mixins.json:MinecraftServerMixin,pl:mixin:APP:byg.mixins.json:access.MinecraftServerAccess,pl:mixin:APP:byg.mixins.json:server.MixinMinecraftServer,pl:mixin:A} at net.minecraft.server.MinecraftServer.m_130011_(MinecraftServer.java:685) ~[server-1.18.2-20220404.173914-srg.jar%23424!/:?] {re:mixin,pl:accesstransformer:B,re:computing_frames,pl:accesstransformer:B,re:classloading,pl:accesstransformer:B,pl:mixin:APP:tetrapak.mixins.json:accessor.MinecraftServerAccessor,pl:mixin:APP:mixin.excavated_variants.json:IMinecraftServerMixin,pl:mixin:APP:balm.mixins.json:MinecraftServerMixin,pl:mixin:APP:byg.mixins.json:access.MinecraftServerAccess,pl:mixin:APP:byg.mixins.json:server.MixinMinecraftServer,pl:mixin:A} at net.minecraft.server.MinecraftServer.m_177918_(MinecraftServer.java:261) ~[server-1.18.2-20220404.173914-srg.jar%23424!/:?] {re:mixin,pl:accesstransformer:B,re:computing_frames,pl:accesstransformer:B,re:classloading,pl:accesstransformer:B,pl:mixin:APP:tetrapak.mixins.json:accessor.MinecraftServerAccessor,pl:mixin:APP:mixin.excavated_variants.json:IMinecraftServerMixin,pl:mixin:APP:balm.mixins.json:MinecraftServerMixin,pl:mixin:APP:byg.mixins.json:access.MinecraftServerAccess,pl:mixin:APP:byg.mixins.json:server.MixinMinecraftServer,pl:mixin:A} at java.lang.Thread.run(Thread.java:833) [?:?] {re:mixin}