I think this server crash -
https://paste.fedoraproject.org/paste/ZcEo12WnyXBTW39Ly9uGOA

May be related to what I saw in console right before it crashed-

[18:17:56] [Server thread/WARN]: Tried to over-fill a container │····························································
[18:17:56] [Server thread/WARN]: Tried to over-fill a container │····························································
[18:17:56] [Server thread/WARN]: Tried to over-fill a container │····························································
[18:18:01] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 4834ms behind, skipping 96 tick(s) │····························································
[18:18:02] [Dungeon Spawner/INFO] [STDOUT]: [futurepack.common.dim.structures.DungeonGeneratorBase:generate:259]: Cant spawn the End Room │····························································
[18:18:02] [Dungeon Spawner/INFO] [STDOUT]: [futurepack.common.dim.structures.DungeonGeneratorBase:generate:225]: Cant gen Boss Room for Lvl 3 │····························································
[18:18:02] [Dungeon Spawner/INFO] [STDOUT]: [futurepack.common.dim.structures.DungeonGeneratorBase:generate:259]: Cant spawn the End Room │····························································
[18:18:03] [Dungeon Spawner/INFO] [STDOUT]: [futurepack.common.dim.structures.DungeonGeneratorBase:generate:259]: Cant spawn the End Room │····························································
[18:18:03] [Dungeon Spawner/INFO] [STDOUT]: [futurepack.common.dim.structures.DungeonGeneratorBase:generate:259]: Cant spawn the End Room │····························································
[18:18:03] [Dungeon Spawner/INFO] [STDOUT]: [futurepack.common.WorldGenTecDungeon$1:run:154]: BlockPos{x=-5999, y=14, z=-2221} │····························································
[18:18:03] [Server thread/ERROR]: Encountered an unexpected exception │····························································
net.minecraft.util.ReportedException: Exception ticking world

https://gist.github.com/ProsperCraft/08c4cb8edc9329206bc886a368cee26f

Interesting, Minecraft itself failed to send the chunk data. The log output only states some debug output, The messages only show random has kind of fucked up. It is kind of proplematic as I dont know what chunk was send, so it is very hard to find out what was causing this. I dont think this was related to the dungeon, but if this keeps happening please notice me.

https://gist.github.com/ProsperCraft/45769a42049671b0878df1a35ec86c19

Could it be related to not being able to spawn rooms?

Well it does not spawn stuff so I dont think so.

you have coremods installed maybe they are doing stuff they shoudnt.

WARNING: coremods are present:
  Land Craft (landcraft-2.2.1.1.jar)
  CTMCorePlugin (CTM-MC1.12-0.2.3.12.jar)
  IELoadingPlugin (ImmersiveEngineering-0.12-76-core.jar)
  Techguns Core (techguns-1.12.2-2.0.1.1.jar)
  OpenEyePlugin (OpenEye-1.12.1-0.8.jar)
  RandomPatches (randompatches-1.12.2-1.0.1.0.jar)
  ShetiPhian-ASM (shetiphiancore-1.12.0-3.5.6.jar)
  Inventory Tweaks Coremod (InventoryTweaks-1.64-dev.jar)
  ForgelinPlugin (Forgelin-1.6.0.jar)
  TransformerLoader (OpenComputers-MC1.12.1-1.7.1.43.jar)
  LoadingPlugin (NoNausea-MC1.12-1.0.jar)
  CoreModLoader (applied-llamagistics-1.12.1-rv5-beta-10.jar)
  BCModPlugin (backpacks 1.12.2 - 3.4.3.jar)
Contact their authors BEFORE contacting forge