I don't know if the source of my problem is the same. If I make a selection (ellips) and afterwards I select 'none' then I see white and black pixel dots on the screen. If I zoom into the picture the dots disappear. I tested it out further and the pixels appear only if I am working on a picture that is zoomed out less than 100%. I don't had this problem in Gimp 2.10.14.
Gimp 2.10.18 / Windows 10
Gimp 2.10.18 / Windows 10