[Bug]: World wont load after reinstalling pack

[CameronJArch]

General Info

• I can reproduce this issue consistently in single-player
• I can reproduce this issue consistently in multi-player
• I have searched for this issue previously and it was either (1) not previously reported, or (2) previously fixed and I am having the same problem.
• I am crashing and can provide my crash report(s)
• I am using the latest version of the modpack

Modpack version

1.0.2

Java version

Java 8 update 261

Modpack Launcher Used

ATLauncher

Memory Allocated

8 GB

Minecraft World Environment

Single Player

Misc Client Info

• Optifine Installed
• Shaders Installed

Server Java Version

No response

Server Operating System

No response

Misc Server Info

• Sponge or Non-Vanilla Forge Server

Issue Description

I load up the instance just fine, and I can create a new world just fine, but If I try loading up my original world it just sits at the loading scree
crash-2021-11-12_21.39.51-server.txt
n.

Additional Information

No response