Comment # 3 on bug 1120639 from Wolfgang Bauer

Ok, after re-reading the mentioned upstream bug report again, it's probably not
really the same issue you see, but rather about the additional brush selection
you get when clicking on the arrow in the popup palette.

Still, please try the krita 4.1.7 package from here which contains the fix.
If it doesn't help, please try the 4.1.60 one as well, which is the latest
snapshot from the upstream 4.1 branch (would show if it is maybe fixed
already).

Another thing I'd try is to disable OpenGL in krita's settings, though I'm not
sure that this could play a part here...