So I've been running a private server with a small group for a bit now. It is modded to high hell, but things have been solid for almost a month of play. All of the sudden I'm getting server crashes and whatever the cause it is above my head when it comes to java. About four times in the last two days I'm getting this exact crash error:

 

---- Minecraft Crash Report ----
// My bad.

Time: 2020-06-29 16:51:47 EDT
Description: Exception in server tick loop

java.util.ConcurrentModificationException
    at java.util.HashMap$HashIterator.nextNode(Unknown Source)
    at java.util.HashMap$KeyIterator.next(Unknown Source)
    at net.minecraft.entity.EntityTracker.tick(EntityTracker.java:290)
    at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:779)
    at net.minecraft.server.dedicated.DedicatedServer.updateTimeLightAndEntities(DedicatedServer.java:397)
    at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:668)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526)
    at java.lang.Thread.run(Unknown Source)

 

The only differing error is showing Jurassicraft as the culprit, which side note someone on the server just started dabbling in. I have no idea if the above crash error and this one could be linked, but if it is then I'm guessing Jurassicraft has got to go.

 

---- Minecraft Crash Report ----
// I blame JurassiCraft Team.

Time: 2020-06-29 08:58:50 EDT
Description: Ticking entity

java.lang.NullPointerException
    at net.minecraft.pathfinding.PathHeap.sortBack(SourceFile:77)
    at net.minecraft.pathfinding.PathHeap.addPoint(SourceFile:22)
    at net.minecraft.pathfinding.PathFinder.findPath(SourceFile:99)
    at net.minecraft.pathfinding.PathFinder.findPath(SourceFile:40)
    at net.minecraft.pathfinding.PathFinder.findPath(SourceFile:30)
    at net.minecraft.pathfinding.PathNavigate.getPathToPos(SourceFile:114)
    at net.minecraft.pathfinding.PathNavigateGround.getPathToPos(SourceFile:51)
    at net.minecraft.pathfinding.PathNavigate.getPathToXYZ(SourceFile:93)
    at net.minecraft.pathfinding.PathNavigate.tryMoveToXYZ(SourceFile:143)
    at org.jurassicraft.server.entity.ai.Family.update(Family.java:91)
    at org.jurassicraft.server.entity.DinosaurEntity.onLivingUpdate(DinosaurEntity.java:951)
    at net.minecraft.entity.EntityLivingBase.TickCentral_TrueOnUpdateTick(EntityLivingBase.java:2179)
    at net.minecraft.entity.EntityLiving.TickCentral_TrueOnUpdateTick(EntityLiving.java:295)
    at org.jurassicraft.server.entity.DinosaurEntity.TickCentral_TrueOnUpdateTick(DinosaurEntity.java:1038)
    at org.jurassicraft.server.entity.dinosaur.BrachiosaurusEntity.TickCentral_TrueOnUpdateTick(BrachiosaurusEntity.java:28)
    at com.github.terminatornl.tickcentral.api.TickHub.trueOnUpdate(TickHub.java:56)
    at com.github.terminatornl.laggoggles.Main.redirectOnUpdate(Main.java:102)
    at org.jurassicraft.server.entity.dinosaur.BrachiosaurusEntity.onUpdate(BrachiosaurusEntity.java)
    at net.minecraft.world.World.updateEntityWithOptionalForce(World.java:1996)
    at net.minecraft.world.WorldServer.updateEntityWithOptionalForce(WorldServer.java:832)
    at net.minecraft.world.World.updateEntity(World.java:1958)
    at net.minecraft.world.World.redirect$updateEntity$zbd000(World.java:4123)
    at net.minecraft.world.World.updateEntities(World.java:1762)
    at net.minecraft.world.WorldServer.updateEntities(WorldServer.java:613)
    at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:767)
    at net.minecraft.server.dedicated.DedicatedServer.updateTimeLightAndEntities(DedicatedServer.java:397)
    at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:668)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526)
    at java.lang.Thread.run(Unknown Source)

 

Any insight, advice, or help is greatly appreciated.

Dont think they support legacy versions im afraid.