I recently built a mod pack ,RLMCC Insanity Unfolds, and Ive been playing it to make sure its stable and playable, these last few days the game has been running fine with the exception of a few player loading quirks here and there but nothing game breaking, fast forward to this morning attempting to load into my survival world results in the game crashing, I will reach 100% on world loading, the joining game prompt will appear, the loading terrain prompt will appear, I get a large lag spike, and then the game says Saving world and then crashes throwing an unknown error in the launcher

when checking the logs I can see that right before the world gets shut down better combat throws a fatal error, I had assumed at first that maybe when the world got shutdown last that something got stuck in an invalid state so I removed the mod and played for a bit to hopefully un-stick whatever it was, no luck there. When I placed the mod back into the game the world continued to crash the game when loading in. I figured that maybe there was a bug introduced in the latest version so I downgraded a couple versions and worked my way back up. The original version of Better Combat the mod pack was using was better combat 1.8.6 - 1.20.1, I tried better combat 1.8.1 - 1.20.1 and worked my way up to version 1.8.5 - 1.20.1, still running into the problem.

Removing Better combat solves the problem but removing the mod renders a major part of my mod pack broken as one of the major aspects of the pack was focused around better combat.
As mentioned the mod pack was working and running stable prior to this morning with Better Combat 1.8.6 - 1.20.1, and there was no change in the mod list this morning

I do not believe that this is a mod compatibility issue as I am still able to generate a new world perfectly fine and the mod pack was working fine these last few days.

The loading issue seems to only occur with my original survival world that I made when I built the mod pack.

 

Here is the last section from my latest.log file

https://pastebin.com/6Q9e9ZLf

 

Same issue without Embeddium/Oculus?

Same problem when removing Sodium Embeddium and oculus
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The game crashed whilst ticking entity Error: java.lang.NullPointerException: Cannot invoke "net.minecraft.client.player.LocalPlayer.getCapability(net.minecraftforge.common.capabilities.Capability)" because "net.minecraft.client.Minecraft.m_91087_().f_91074_" is null

Edited November 24, 2024Nov 24 by Veradigm
Added error output from minecraft launcher for further context

Add the full crash-report

 

Here is the latest crash report

https://pastebin.com/nY0cMGkX

Remove Just Leveling! It tries to work with capability that equals to null.

Edited November 24, 2024Nov 24 by R4L

That fixed it