Do Apple Silicon Macs have an option like Intel Macs where you can reset PRAM, or SMC? Often times when things go wrong that don't resolve on an OS level is because there are corrupted settings in PRAM, and a reset fixes those many times. Not saying it will make a difference, but people like
@likegadgets who are still continuing to be unsuccessful with a backup, or even those having to exclude Find My items to get it to work might consider if there is a way to make sure there isn't bad data being picked up that may need to be cleared. I don't own an Apple Silicon mac, so I don't know if the options and functions I'm suggesting exist on that platform. I'm just saying "if they do" might be worth giving it a shot to see if it helps.