How clone a Time Machine backup APFS volume?

I have a three months old external LaCie D2 Professional drive with two volumes, one being a TM. I installed it just after having installed Big Sur at the time. I never had any issues with Catalina and an older drive but this combination seems to be causing problems.

Whenever it is mounted it is constantly spinning (literally for hours). Culprit looks to be a lot of mdworker processes. Unmounting the TM volume resolves the situation but of course that is not a solution. I am starting to fear it will get worn out. The LaCie drive seems to be ok, it has the latest firmware driver. Unless there is something wrong with the drive it self (Disk Utility's First Aid tool says there are issues with the drive but Disk Utility in Recovery mode says the drive is ok) I wonder if this is just one more problem introduced by Big Sur which seems to be the worst upgrade in years...

I would like to restore the drive from scratch but need to get the TM backups over to another drive. How can this be done? I tried to drag/drop but that doesn't work. The restore and image features in Disk Utility error. So I am a bit at a loss and am not doing backups right now...