Conflict resolved: error loading chunks and freezing issues fixed; the loading process was stalling due to a conflict between Terralith and structure mods.

The Longwings mod overloads entities, causing uncontrolled loading.

Leawind's Third Person mod caused player movement to stutter and lowered the FPS.

Removed

Leawind's Third Person

https://www.curseforge.com/minecraft/mc-mods/leawind-third-person

Longwings

https://www.curseforge.com/minecraft/mc-mods/longwings

Terralith

https://www.curseforge.com/minecraft/mc-mods/terralith

IMPORTANT

Backup your data before downloading.