After moving the screen, writing renders incorrect.

[piiskop]

If I have more things on the screen than fit vertically in the visible area, and I move down and right after that write something then the writing will be rendered incorrect. For instance, I try to write 2 but only a stroke appears. Sometimes it takes some time for that anomaly to happen. It only happens once and after that, I can write normally again. Once I move the screen again and write something the same anomaly happens.