its something to do with packets i think after you create 3 worlds and log into each world 1 at a time it usually kicks back to the multiplayer menu after 3rd world for some reason im playing single player https://mclo.gs/R87jh7A

im running latest version off of discord i tested the version from curseforge latest one and while loading a world the client just closes out without crashing all instability in my mod pack is gone after removing this mod i would love to include it in the modpack im working on but i cant. ill use mchelie until this is fixed . i appreciate you making this mod though maybe it works by itself .

Scratch everything it wasn't this mod making the client close out it's several mods doing it . Does every mod pack made create multiple worlds and log into them all multiple times without the client closing out

Something is removing entities during the packet handling. This shouldn't ever happen on MC 1.12.2 since the packet handling always happens on the same thread in a linear state. If a mod is allowing concurrent execution, then that's just going to happen. Mind you, a bad packet shouldn't crash things. That's custom mod behavior. Usually VanillaFix causes this, but you don't have that so it must be some other mod crashing for a bad packet.

java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
at java.util.ArrayList$Itr.next(Unknown Source)
at mcinterface1122.WrapperWorld.getExternalEntity(WrapperWorld.java:217)
at mcinterface1122.WrapperWorld.getExternalEntity(WrapperWorld.java:98)
at minecrafttransportsimulator.packets.components.APacketPlayer.handle(APacketPlayer.java:40)