When loading a world, CURRENCY_ADD_EVENT.invoke() seems to be doing something that Fabric doesn't like, and it's causing the server to hang.
https://pastebin.com/rJNT3Jax
Sorry I ended up making the pastebin'd error really hard to read.

Enabled Mods:
GUI Shop by UnsafeDodo - latest 1.20.2 version
EightsEconomyP - latest 1.20.2 version
OctoEconomyApi - 1.0.1
Nether Portal Fix - latest 1.20.2 version
Balm - latest 1.20.2 version
fabric-permissions-api - latest 1.20.2 version
sgui - latest 1.20.2 version
polymer - latest 1.20.2 version
Fabric API - latest 1.20.2 version
Text Placeholder API - latest 1.20.2 version