DISPLAY NOT SUPPORTED AFTER UPDATE TO BIG SUR 11.2 - WORKED FINE ON USB-C TO VGA ADAPTOR ON 11.1

I had read about the display issues some people were having, HDMI connected displays/to VGA adaptors not working under 11.1, and the 11.2 update solving them.

My issue is the other way round, my admitedly old AOC VGA display worked fine plugged in to a VGA to USB-C adaptor, until I upgraded the OS to 11.2.

Now the display has a floating "input not supported" box moving all over the screen, and although desktop displayed on screen, all icons were tiny, and changing dispaly settings didn't help, they got bigger but desktop overlapped monitor screen. Then after a restart, screen has same floating box message, but desktop image is flickering on and off every 2/3 seconds.

This is frustating to say the least, don't want to have to buy a new display as this defeats the oject of a mac mini using exsisting hardware, my old 2010 mac mini worked fine with this dispaly for years.

Any suggestions? Can I roll back to 11.1? Or may it be an adaptor issue? HDMI adaptor still doesn't work either.

Al.