Mouse becomes disabled after switching off with pen

I discovered MyPaint and I love it so much for its infinite canvas and brushes. Ideal combination for art sketches and storyboards for animation and so. But one bug bugs me so much and it seems ancient.

When I press with pen outside mypaint window, making it’s inactive and then go back with pen or mouse, mouse clicks become non-working at all. Both left and right. I recreated this behavior several times. If I press outside with pen and return with pen or mouse - mouse stops effectively working. Only pen registers its clicks. Also mouse works as device, I can move cursor, but app doesn’t see it - checked with input device logging window.
I have win 10 x64 and simplest wacom intuos s.
I will continue to use it anyway, but if there is a slightest chance to fix this I’d be infinitely happy.