DND29 said

Top screenshot : hardware acceleration is enable. Bottom screenshot : hardware acceleration is disable. when last year, this problem was not happend.

Check to see if newer video drivers are available for that PC.

Did you try to update the graphics display driver?

• https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

The graphics display driver is lastest one.

I guess that you'll need to keep hardware acceleration disabled.

If you can provide detailed information about your video / graphics hardware and the version number of the drivers involved from about:support (typed in the Location Bar), we can look into existing Bug reports or create a new Bug report for you.