Server lag

[GT86]

I have had Botania mod installed before, but for some reason I removed it. The world follows my use of /fml confirm to allow him to skip these blocks. I don’t know if this is a sequela. Now it only has Pixelmon 6.3.1 and some plugins installed.

The server will lag for a while, server console appears this message

[Server] Server thread/WARN Tried to add entity minecraft:item but it was marked as removed already

and server crash

@GT86

Server thread/FATAL Error executing task
java.util.concurrent.ExecutionException: java.lang.IndexOutOfBoundsException: Index: 101, Size: 46
at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:1.8.0_171]
at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[?:1.8.0_171]
at net.minecraft.util.Util.func_181617_a(SourceFile:47) [h.class:?]
at org.spongepowered.common.SpongeImplHooks.onUtilRunTask(SpongeImplHooks.java:284) [SpongeImplHooks.class:1.12.2-2705-7.1.0-BETA-3171]
at net.minecraft.server.MinecraftServer.redirect$onRun$zjf000(MinecraftServer.java:3987) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:723) [MinecraftServer.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:396) [nz.class:?]
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:668) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526) [MinecraftServer.class:?]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_171]
Caused by: java.lang.IndexOutOfBoundsException: Index: 101, Size: 46
at java.util.ArrayList.rangeCheck(ArrayList.java:657) ~[?:1.8.0_171]
at java.util.ArrayList.get(ArrayList.java:433) ~[?:1.8.0_171]
at net.minecraft.inventory.Container.func_184996_a(Container.java:258) ~[afr.class:?]
at net.minecraft.inventory.ContainerPlayer.func_184996_a(ContainerPlayer.java:545) ~[agi.class:?]
at net.minecraft.network.NetHandlerPlayServer.func_147351_a(NetHandlerPlayServer.java:1158) ~[pa.class:?]
at net.minecraft.network.play.client.CPacketClickWindow.func_148833_a(CPacketClickWindow.java:38) ~[lf.class:?]
at net.minecraft.network.play.client.CPacketClickWindow.func_148833_a(CPacketClickWindow.java:12) ~[lf.class:?]
at org.spongepowered.common.network.PacketUtil.onProcessPacket(PacketUtil.java:148) ~[PacketUtil.class:1.12.2-2705-7.1.0-BETA-3171]
at net.minecraft.network.PacketThreadUtil$1.redirect$onProcessPacket$zla000(SourceFile:539) ~[hv$1.class:?]
at net.minecraft.network.PacketThreadUtil$1.run(SourceFile:13) ~[hv$1.class:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_171]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[?:1.8.0_171]
at net.minecraft.util.Util.func_181617_a(SourceFile:46) ~[h.class:?]
… 7 more