If you switch between layers or other parts of the program only some parts a painted new and the rest of the screen doesn't change. For example you change the lay from channel "1 to 24" to "25 to 32" then you get 8 channels well painted but the other channels which were displayed before you see (but you cannot interact with them).
The program is running on big monitor with a resolution 3840x2160 (there is another monitor (build in notebook monitor) with 1920x1080 on the same system).
If I use another application windows to wipe over the area which is not cleared it has no effekt. (This would produce paint commands to the area)