It’s not displaying the image that’s the problem.
Also, I’ve tried it with Canvas Graphics Acceleration disabled and that had no effect on drawing or on appearance.
You could try updating your graphics tablet driver and then remaking its configurations/settings.
(Hello @sooz 
)
You could also try the version 5.2 Release Candidate. I’d suggest the portable .zip package for Windows:
Krita 5.2 Release Candidate is out! Please help us in another round of testing!
https://download.kde.org/unstable/krita/5.2.0-rc1/krita-x64-5.2.0-rc1.zip
Then see if that improves the situation.
Edit:Add:
Are you running another demanding application, such as transcoding a large video in the background as you work with krita?