Time Machine couldn’t complete the backup: Two of the disks to back up have the same name. (Catalina) I have erased my backup hard drive and get the following error when I attempt my first backup:

My disks look like this

I'm running 10.15. Any ideas appreciated.
I had the same issue but this because I truly had 2 "Macintosh HD":



I renamed one of the two and the problem was solved: