Forgot to say, 109 32 bit on Raspberry Pi 3B+ with hardware acceleration enabled does not show this issue.

Some graphics drivers and graphics cards may cause the Firefox browser to freeze often especially when using hardware acceleration. Hardware acceleration forces some computer functions to run efficiently compared to using software on a general-purpose CPU.

Thanks techguy150, while I appreciate your comment, the fact the system worked flawlessly for several years prior to version 109 made me wish to make the issue aware to the community, it being the only element of change.

Maybe try to ask about this on the RPi support forum as they most likely know more about running 64 bit Firefox on their OS.