Hello. I've recently given krita another shot and experienced this weird bug. I think I've had it in other programs before - but can't replicate it in anything else right now.
It's hard to explain with words so here's a video: https://youtu.be/UvbCADbzTck
I'm using a Wacom Intuos Pen Small (CTL-480). Latest drivers, almost completely fresh windows 10 install, and downloaded Krita a couple hours ago. Disabled any stupid windows settings (like the Wacom "use windows ink" and such that has worked for others) and nothing.

EDIT: Fixed. Went to Wacom Tablet Properties, specifically added krita as an Application, then disabled Windows Ink. Not sure if this is worth keeping around, noone else seems to have had this issue. Delete me ))