Demonstrated on https://www.youtube.com/watch?v=Dsv15No_IgE
(see video description for configuration of that instance)
I was not able to find a root cause, but the behavior can be observed in the video when I edit the paragraph starting at 2:39.
Note: I'm working on an external keyboard, hands off the mouse, and no trackpad anywhere close to my hands.
Expected behavior: The cursor shouldn't jump