Sam is the wise one who recommended this raid 
seems all ok now if I restart computer - apparently it was the update that threw it into a tizzy and having another external drive connected seems to have also upset the delicate balance - who knew…thanks for all the valuable feedback! another “warning will robinson” haha
I see that MacOS 12.3 was released today. Anybody going to try it? I’m especially interested in M1 Max chip systems…