It can be fixed! Fix:
Press ESC → Edit Mode → Layout → NEW LAYOUT, and rebuild from scratch.
Thank you to Jetfire, Styleboy,Iraeliis and anyone else who found the fix. Not sure if it was in Kaivax’s post originally and I just missed it due to not understanding what they ment by Loadout.
Not going to test with any bar addons for the time being.
See you in Azeroth, with Actions.