Brilliant Saffith.
Sorry to keep piling these up, but at least I'm finding things. I would never have noticed this one, had I not been testing a game with this QR enabled. (It's usually a sin of quest design.)
At first I thought it was some kind of script bug, but there were no scripts on the screen. It instantly dawned on me that the quest had Smart Scrolling, and when I disabled it, and the bug stopped, I had a very good idea of what was happening. It couldn't read datum that wasn't there, and was either overflowing, or corrupting the stack.
