Same exact issue. No fix. I keep multiple clones (use CCC), so I just started over. I'm using SanDisk 2TB Extreme Portable External SSD Up to 550MB/s USB-C, USB 3.1 btw. I'm thinking I need to up my clones to 4. Absurd, but this is the second fail. The first one was not like this issue (com.apple.DiskManagement.disenter error 49218), but a PITA all the same.