Had just tested it again making sure I made a clean world on Aternos with version 1.3 instead of uploading a world like last time. I'm not sure what's causing the issue if the seed in the overworld.json file hasn't changed.
Basically world has generated with massive chunk error issues upon updating to version 1.3.2 of Another Quality Modpack 2. I think it's a server-side issue but I wouldn't know how to suggest fixing it, might be better to disable the modpack altogether.
I've tested this myself with updating a client side version of the modpack and encountered no issues and made sure the overworld.json seed had not changed in between updates.
I've also provided an image showing how this looks in-game on an Aternos server.