OK, thanks, and yes I am using 1.7.0rc1. I've only made one print, but that went well
The things I noticed were this. I backed up my octoprint then downloaded and installed 1.7.0rc1 and as expected was prompted to upgrade to python3. Found the FAQ to install 0.18 to get Python3. I downloaded the Raspberry Pi Imager and and followed the update instructions on the site. When I ran the imager I used Shift-Ctl-X first to set the WPA SSID and passphrase. While there I enabled SSH. Then used the procedure to burn 0.18 to a card.
This all went fine. When I put the card in the Pi and booted it seemed ok until I tried to connect (I use Putty on Windows). No connection via IP address. I looked in the management interface of my router and I saw a new device on an odd IP address in the connected devices list. I have a DHCP address reservation for OctoPi and that address did not appear.
So, I figured I mucked something up in the Imager and started over. The odd thing I found was when I used Shift-Ctrl-X the preshared wifi key, which has an ampersand (&) in it and the string displayed was 'xxxxxx;amp&xxxxxx' with the ';amp' inserted as I didn't enter it. So I went into the router and changed the PSK to a simple combination of dictionary words and entered this into the Shift-Ctrl-X interface and wrote the image to the card. Booted the Pi with the new imaged and all worked well. Picked up the reserved DHCP address from the router so I used SSH to connect to the OctoPi and used raspi-config to reconfigure the PSK and got everything back the way it was.
When I tried to install the 1.7.0rc1 backup got an error message that the backup was a newer version that what was installed (1.5.x I think in the Pi Imager program?) So I upgraded to 1.7.0rc1 and then was able to restore my original backup.
After this little hiccup all worked well.