Commands don't work and game locks when saving.

[BigGram]

I've run into a issue where Minecraft instances running Forge don't allow for the usage of commands (/help, /gamemode, /seed to list a few) even if the world is generated with cheats enabled, (I've already checked to make sure world are actually generating with cheats enabled using NBTExplorer). Cheats do work if I enable them when opening to LAN. Furthermore the game locks when the saving and exiting (specifically at the "Saving world" screen.) When I forcefully killed the instance and re-opened the world everything I did; place blocks, drop items etc... has been properly saved. 

This issue occurred in Forge versions 35.0.10 | 35.1.4 | 35.1.37 (running in 1.16.4), as well as Forge 31.2.0 (running 1.15.2). Optifine hasn't been installed, the only mods that have been installed are WorldEdit & WorldEditCUI. However these issues didn't go away when I disabled them both and still occurred just running Forge. This doesn't happen when running a Vanilla instance; and uninstalling Forge from the the bugged instances fixes the issues. Minecraft is running with x64 java at the latest version so I'm sure its not that. 

These issues suddenly appeared and I can't think of anything I could have done the cause them. So I've run out of ideas, any help would be greatly appreciated.

I don't have any crash reports because despite these issues that the game seems to run stable.

Edited February 11, 2021 by BigGram

[BigGram]

Issue seems to be with the MultiMC launcher, still don't know specifics but the issue isn't Forge itself.