[todivefor]

I have a problem, probably user created. I am running a Macbook Air M1 with Monterey 12.1. I backup weekly alternately to MacbookProOdd and MacbookProEven with SD 3.5. MacbookProEven contains backup of system 11.6.2 and MacbooProEven is last nights backup 12.1. External is USB 3.0.

I've searched and get mixed comments as to whether or not a USB 3.0 drive can be made bootable in this environment. I wanted to archive my 11.6.2 backup and tried going from external to external. I thought I could do this, but told no. Next I tried booting to this backup and was successful, but it was so slow, I gave up. Now I can't boot from either 11.6.2 or last nights 12.1 backup. Both get about a third of the way through the boot progress bar and then reboot to the system drive. I tried setting the 11.6.2 disk to my startup disk and got the attached message.

Probably need better backup media?