On December 7, 2020 at 04:42, Twelfth Monkey said...
'Twas old firmware - updated and sorted.
To paraphrase Marvin from The Hitchhikers' Guide to the Galaxy, I hope it doesn't hurt having to think down to my level!
Well that's great news! I'm also happy that my post above also describes how to diagnose if a scroll wheel is physically broken. :-)