When zooming in and out while in-game, white border may appear around the level. This disappears as soon as any attempt to scroll is made, though this results in the screen scrolling "jumping" considerably.
As far as I remember (did not actually test), this did not occur in the stable version. (EDIT: Tested now; I cannot replicate this issue in the stable version.)
Just in case, the level I specifically triggered this on was Smooth 3 "Splatwire" of LPIV (unmodified, apart from converting to new format).
I can confirm this; it happened to me one of Clam's levels.
I have also encountered something else similar:
When scrolling using the mini-map (only) the game screen flashes, particularly around the edges.
I introduced this bug in version 11.15.22 when I coded zooming in at the cursor position and fixed it in 11.15.23. If I forgot some cases and it still happens, then I would appreciate a more detailed report how to reproduce it.