I died from a Zombie but it doesn't matter at all! When i die it always freezes the game and i must stop the game from Task Manager, it really sucks...

Log Part:

[23:01:42] [Render thread/FATAL]: Error executing task on Client
java.lang.IllegalArgumentException: Player etaPreD is missing a damage model!
at ichttt.mods.firstaid.common.util.CommonUtils.lambda$getDamageModel$1(CommonUtils.java:167) ~[firstaid:1.9.7]
at ichttt.mods.firstaid.common.util.CommonUtils$$Lambda$16672/0x0000000000000000.get(Unknown Source) ~[?:?]
at net.minecraftforge.common.util.LazyOptional.orElseThrow(LazyOptional.java:296) ~[forge:?]
at ichttt.mods.firstaid.common.util.CommonUtils.getDamageModel(CommonUtils.java:167) ~[firstaid:1.9.7]
at ichttt.mods.firstaid.common.network.MessageAddHealth$Handler.lambda$onMessage$0(MessageAddHealth.java:57) ~[firstaid:1.9.7]
at ichttt.mods.firstaid.common.network.MessageAddHealth$Handler$$Lambda$20647/0x0000000000000000.run(Unknown Source) ~[?:?]
at net.minecraftforge.fml.network.NetworkEvent$Context.enqueueWork(NetworkEvent.java:215) ~[forge:?]
at ichttt.mods.firstaid.common.network.MessageAddHealth$Handler.onMessage(MessageAddHealth.java:55) ~[firstaid:1.9.7]
at ichttt.mods.firstaid.FirstAid.lambda$init$12(FirstAid.java:141) ~[firstaid:1.9.7]
at ichttt.mods.firstaid.FirstAid$$Lambda$14093/0x0000000000000000.accept(Unknown Source) ~[?:?]
at net.minecraftforge.fml.network.simple.IndexedMessageCodec.lambda$tryDecode$3(IndexedMessageCodec.java:128) ~[forge:?]
at net.minecraftforge.fml.network.simple.IndexedMessageCodec$$Lambda$20163/0x0000000000000000.accept(Unknown Source) ~[?:?]
at java.util.Optional.ifPresent(Optional.java:159) ~[?:1.8.0_292]
at net.minecraftforge.fml.network.simple.IndexedMessageCodec.tryDecode(IndexedMessageCodec.java:128) ~[forge:?]
at net.minecraftforge.fml.network.simple.IndexedMessageCodec.consume(IndexedMessageCodec.java:162) ~[forge:?]
at net.minecraftforge.fml.network.simple.SimpleChannel.networkEventListener(SimpleChannel.java:80) ~[forge:?]
at net.minecraftforge.fml.network.simple.SimpleChannel$$Lambda$2797/0x0000000000000000.accept(Unknown Source) ~[?:?]
at net.minecraftforge.eventbus.EventBus.doCastFilter(EventBus.java:247) ~[eventbus-4.0.0.jar:?]
at net.minecraftforge.eventbus.EventBus.lambda$addListener$11(EventBus.java:239) ~[eventbus-4.0.0.jar:?]
at net.minecraftforge.eventbus.EventBus$$Lambda$2799/0x0000000000000000.invoke(Unknown Source) ~[?:?]
at net.minecraftforge.eventbus.EventBus$$Lambda$2437/0x0000000000000000.invoke(Unknown Source) ~[?:?]
at net.minecraftforge.eventbus.EventBus.post(EventBus.java:302) ~[eventbus-4.0.0.jar:?]
at net.minecraftforge.eventbus.EventBus.post(EventBus.java:283) ~[eventbus-4.0.0.jar:?]
at net.minecraftforge.fml.network.NetworkInstance.dispatch(NetworkInstance.java:86) ~[forge:?]
at net.minecraftforge.fml.network.NetworkHooks.lambda$onCustomPayload$1(NetworkHooks.java:91) ~[forge:?]
at net.minecraftforge.fml.network.NetworkHooks$$Lambda$20147/0x0000000000000000.apply(Unknown Source) ~[?:?]
at java.util.Optional.map(Optional.java:215) ~[?:1.8.0_292]
at net.minecraftforge.fml.network.NetworkHooks.onCustomPayload(NetworkHooks.java:91) ~[forge:?]
at net.minecraft.client.network.play.ClientPlayNetHandler.func_147240_a(ClientPlayNetHandler.java:1904) ~[?:?]
at net.minecraft.network.play.server.SCustomPayloadPlayPacket.func_148833_a(SCustomPayloadPlayPacket.java:59) ~[?:?]
at net.minecraft.network.play.server.SCustomPayloadPlayPacket.func_148833_a(SCustomPayloadPlayPacket.java:11) ~[?:?]
at net.minecraft.network.PacketThreadUtil.func_225383_a(SourceFile:21) ~[?:?]
at net.minecraft.network.PacketThreadUtil$$Lambda$20521/0x0000000000000000.run(Unknown Source) ~[?:?]
at net.minecraft.util.concurrent.ThreadTaskExecutor.func_213166_h(SourceFile:144) [?:?]
at net.minecraft.util.concurrent.RecursiveEventLoop.func_213166_h(SourceFile:23) [?:?]
at net.minecraft.util.concurrent.ThreadTaskExecutor.func_213168_p(SourceFile:118) [?:?]
at net.minecraft.util.concurrent.ThreadTaskExecutor.func_213160_bf(SourceFile:103) [?:?]
at net.minecraft.client.Minecraft.func_195542_b(Minecraft.java:947) [?:?]
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:607) [?:?]
at net.minecraft.client.main.Main.main(Main.java:184) [?:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_292]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_292]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_292]
at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_292]
at net.minecraftforge.fml.loading.FMLClientLaunchProvider.lambda$launchService$0(FMLClientLaunchProvider.java:51) [forge-1.16.5-36.2.2.jar:36.2]
at net.minecraftforge.fml.loading.FMLClientLaunchProvider$$Lambda$480/0x0000000000000000.call(Unknown Source) [forge-1.16.5-36.2.2.jar:36.2]
at cpw.mods.modlauncher.LaunchServiceHandlerDecorator.launch(LaunchServiceHandlerDecorator.java:37) [modlauncher-8.0.9.jar:?]
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:54) [modlauncher-8.0.9.jar:?]
at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:72) [modlauncher-8.0.9.jar:?]
at cpw.mods.modlauncher.Launcher.run(Launcher.java:82) [modlauncher-8.0.9.jar:?]
at cpw.mods.modlauncher.Launcher.main(Launcher.java:66) [modlauncher-8.0.9.jar:?]

I need more details. Were you playing on a server? Had the server the mod as well? What version of the mod did you use? What version of forge?

I also have this problem too.
Only when playing on the server. It crashes every time when the player dies and respawns.
I use the latest mod version of 1.16.5 and MohistMC.

Here is my server log.
https://pastebin.com/zpPj2NDS

I don't support custom server software. It's always a pain to debug issues with Mohist and other hybrid servers. Only forge servers are officially supported, sorry