HI, i have been with this issue since i started a modded server with my friends and sometimes with no reason at all, it crash. This problem only happens when u try to enter into the server, sometimes i gotta reset or try a few times before i can join the game without the crash, and everything works perfectly until u disconnect or other player wants to join the world and have the same issue, so sometimes you can enter at the first attempt or u cant even after trying 6 times, however this is the log:

java.lang.IllegalStateException: Tag witherstormmod:wither_sickness_immune used before it was bound
    at net.minecraft.tags.TagRegistry$NamedTag.func_232944_c_(TagRegistry.java:131) ~[?:?] {re:classloading,pl:accesstransformer:B}
    at net.minecraft.tags.TagRegistry$NamedTag.func_230235_a_(TagRegistry.java:142) ~[?:?] {re:classloading,pl:accesstransformer:B}
    at net.minecraft.entity.EntityType.func_220341_a(EntityType.java:542) ~[?:?] {re:classloading,pl:accesstransformer:B,re:mixin,pl:accesstransformer:B}
    at nonamecrackers2.witherstormmod.common.capability.WitherSicknessTracker.isActuallyImmune(WitherSicknessTracker.java:597) ~[?:1.16.5-1.0.2.4] {re:classloading}
    at nonamecrackers2.witherstormmod.common.capability.WitherSicknessTracker.tick(WitherSicknessTracker.java:186) ~[?:1.16.5-1.0.2.4] {re:classloading}
    at nonamecrackers2.witherstormmod.client.event.ClientWitherSicknessEvents.lambda$onClientTick$0(ClientWitherSicknessEvents.java:31) ~[?:1.16.5-1.0.2.4] {re:classloading}
    at nonamecrackers2.witherstormmod.client.event.ClientWitherSicknessEvents$$Lambda$36998/1295085643.accept(Unknown Source) ~[?:?] {}
    at net.minecraftforge.common.util.LazyOptional.ifPresent(LazyOptional.java:151) ~[?:?] {re:mixin,re:classloading}
    at nonamecrackers2.witherstormmod.client.event.ClientWitherSicknessEvents.onClientTick(ClientWitherSicknessEvents.java:29) ~[?:1.16.5-1.0.2.4] {re:classloading}
    at net.minecraftforge.eventbus.ASMEventHandler_3127_ClientWitherSicknessEvents_onClientTick_ClientTickEvent.invoke(.dynamic) ~[?:?] {}
    at net.minecraftforge.eventbus.ASMEventHandler.invoke(ASMEventHandler.java:85) ~[eventbus-4.0.0.jar:?] {}
    at net.minecraftforge.eventbus.EventBus$$Lambda$3172/812598172.invoke(Unknown Source) ~[?:?] {}
    at net.minecraftforge.eventbus.EventBus.post(EventBus.java:302) ~[eventbus-4.0.0.jar:?] {}
    at net.minecraftforge.eventbus.EventBus.post(EventBus.java:283) ~[eventbus-4.0.0.jar:?] {}
    at net.minecraftforge.fml.hooks.BasicEventHooks.onPostClientTick(BasicEventHooks.java:96) ~[?:?] {re:classloading}
    at net.minecraft.client.Minecraft.func_71407_l(Minecraft.java:1544) ~[?:?] {re:mixin,pl:accesstransformer:B,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:mixin:A,pl:runtimedistcleaner:A}
    at net.minecraft.client.Minecraft.func_195542_b(Minecraft.java:954) [?:?] {re:mixin,pl:accesstransformer:B,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:mixin:A,pl:runtimedistcleaner:A}
    at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:607) [?:?] {re:mixin,pl:accesstransformer:B,pl:runtimedistcleaner:A,re:classloading,pl:accesstransformer:B,pl:mixin:A,pl:runtimedistcleaner:A}
    at net.minecraft.client.main.Main.main(Main.java:184) [?:?] {re:classloading,pl:runtimedistcleaner:A}
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_51] {}
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_51] {}
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_51] {}
    at java.lang.reflect.Method.invoke(Method.java:497) ~[?:1.8.0_51] {}
    at net.minecraftforge.fml.loading.FMLClientLaunchProvider.lambda$launchService$0(FMLClientLaunchProvider.java:37) [forge-1.16.5-36.2.39.jar:36.2] {}
    at net.minecraftforge.fml.loading.FMLClientLaunchProvider$$Lambda$512/471031651.call(Unknown Source) [forge-1.16.5-36.2.39.jar:36.2] {}
    at cpw.mods.modlauncher.LaunchServiceHandlerDecorator.launch(LaunchServiceHandlerDecorator.java:37) [modlauncher-8.1.3.jar:?] {}
    at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:54) [modlauncher-8.1.3.jar:?] {}
    at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:72) [modlauncher-8.1.3.jar:?] {}
    at cpw.mods.modlauncher.Launcher.run(Launcher.java:82) [modlauncher-8.1.3.jar:?] {re:classloading}
    at cpw.mods.modlauncher.Launcher.main(Launcher.java:66) [modlauncher-8.1.3.jar:?] {re:classloading}
 

im not the better on this things but i surely know that this is not a problem with an entity spawning on the chunk bcs even that other players can play while i cant, they go to my zone and dont get any problem. hopes this get fixed easy and fast, ty in advance

It seems that the problem is with the "Wither Sickness" effect. The only solution I can think of is to disable it in the config and use an nbt editor to remove the effect manually.

The version you are using is no longer supported on this forum.

Please update to a modern version of Minecraft to receive support.

Currently supported versions are 1.19.3 (Latest), 1.19.2, and 1.18.2 (LTS).