On Sep 17, 2021, at 19:31, Alan Third <alan@idiocy.org> wrote:

Nobody has any idea what they were doing when it happened? Scrolling
or typing or resizing windows or anything?

Someone in an unrelated bug report suggested something similar
happened after they created a new frame (which doesn't make much
sense, unless Emacs is drawing to the wrong frame). Was anyone doing
anything like that? Child frames popping up for use with, I don't
know, company mode or something?

Where on the frame do these things happen? If it happens again please
send a screenshot of the whole frame.
--
Alan Third

I just had this happen to me as well, screenshots attached. I wasn’t switching buffers, just scrolling with the mouse wheel. The visible frame is the only frame (it’s in fullscreen) and there were no other frames since I started emacs.

I tried scrolling some of the bugged “as” out of the view and scrolling back, they were still there.