Today's git master of Plasma 6 Wayland built form source on top of Fedora KDE 39.


STEPS TO REPRODUCE
1. Have two screens, and arrange them in the KScreen KCM horizontally so that they are touching
2. Unplug the screen on the right
3. Raise the scale factor of the screen on the left (e.g. from 200% to 225% in my case)
4. Plug in the second screen again


OBSERVED RESULT
There is now a gap between the screens and the cursor can't cross the gap from one screen to the other! The KCM displays a warning message about this, as though I somehow did it on purpose. :) 


EXPECTED RESULT
The screens keep touching on their common edge


ADDITIONAL INFORMATION
Does not happen if the secondary screen has never been connected before (or at least, if there are no pre-existing KScreen configs for it). It only happens if the prior KScreen config for the secondary screen is available for use. What happens is that the secondary screen's prior absolute position is retained, despite that absolute position no longer resulting in it touching the primary screen anymore.