I use PS for illustration and every now and again, photoshop decides to insert random black fills all over the place. If I try to undo, they're still there, and if I go back several steps in history they're still there. They can't be deleted or repaired, so I have to discard everything and start again. I can't identify any particular action that sets it off, it just appears out of nowhere. I'm using Photoshop 22.0.1 on a 2013 iMac with 24gb ram, Catalina 10.15.7 with a Wacom Cintiq Pro. If anyone could give me a clue as to why it might be happening, and what I could do to prevent it, I'd be very grateful.