Trying to understand what's happening and not getting very far so returning to see if someone will explain the ins and outs to me. A while ago I was told to stop using my WIFI repeater. It does seem to have reduced the frequency of problems - although not totally vanquished them. So I looked at the extender in more depth and tried it as an access point. Had a problem today so I'm still pondering my options. I can revert to 2.4G WIFI at the other end of the house - but obviously prefer to stay with 5G.
I figure that the advice to stop using the extender was based on something - but there were not other details. So am hoping someone can flesh it out for me.