Firefox restore from fullscreen issue



If watching any video in full screen, upon restoring Firefox back to "normal view" the entire program changes its position on my monitor.
In regular mode (IE; not full screen) the position of the program on the screen - flush with my top and bottom panels - but NOT full screen is unaffected when closing and re-opening Firefox.
The change in screen position is only when going from full screen view to non-full screen mode.
OS: Ubuntu MATE 22.04.4 LTS 64 bit
Firefox Ver: 115.14.0 ESR 64bit

Hopefully someone can help.
Cheers

software 22-04-jammy-LTS