Minecraft 1.20.1
Forge 47.3.10
CodeChickenLib 4.4.0.516
Crash was by a user of my modpack. Crash occured when player tried to open an existing world. Was able to load a backup and join world with no issue. Crash log points to CodeChickenLib as a possible suspect.
Crashlog: https://pastebin.com/XezxcgQE
Thanks!