Am 16.12.21 um 16:00 schrieb Haines Brown:
> A recent upgrade installed the new version of Firefox: 78.15.0esr.
> It was released on 5 Oct 2021.
>
> It has a very annoying behavior and I wonder if others experience
> it. I have torbrowser installed. It works fine, and so I don't think
> it is a problem with X window system. I purged Firefox and
> reinstalled it with no custsomization, and it still showed the
> behavior. So it seems part of the Firefox release itself.
>
> The behavior is hard to describe. When I scoll text up or down by
> using the arrow keys, the lines of text begin to break up and
> become unreadable until they settle about one second after the
> scroll ends. Actually it is thin horizontal white lines less
> than a cm wide that last a second. Nowhere else do I have
> this problem with scrolling.
>
> Another symptom: when the cursor is moved to or away from the
> scroll bar, the grey scrollbar is broken into a vertical set of
> grey and light grey lines for about a second. When I drag the
> scrollbar to scroll text, text and images are broken up by
> horizontal white linees for a about a second. In a colored
> image these lines can be colors from the image.
>

Sounds like a bug with the refreshing.
Does anything change when you cover the area temparly with an other window ?