Time Machine issue

[Frixos]

I have a WD external HDD that I got back in December and had been using just fine with my 2013 MBP on Catalina. I just updated to the M1 MBA and Big Sur 11.5, and I keep getting errors with TM.
At the end of backing up, it says: "Time Machine couldn’t complete the backup to “WD Time Machine” Unable to complete backup. An error occurred while creating the backup folder."

I've tried to re-format the drive - APFS (Case-sensitive, Encrypted), without the issue being fixed. I cannot repair the drive (see attached):

Edit - I managed to figure it out!

 

[0128672]

I have a WD external HDD that I got back in December and had been using just fine with my 2013 MBP on Catalina. I just updated to the M1 MBA and Big Sur 11.5, and I keep getting errors with TM.
At the end of backing up, it says: "Time Machine couldn’t complete the backup to “WD Time Machine” Unable to complete backup. An error occurred while creating the backup folder."

I've tried to re-format the drive - APFS (Case-sensitive, Encrypted), without the issue being fixed. I cannot repair the drive (see attached):

Edit - I managed to figure it out!

It could be very helpful to other users if you post your solution (and also change the title to use the Resolved tag).

 

[Frixos]

It could be very helpful to other users if you post your solution (and also change the title to use the Resolved tag).

This is a standard HDD and for some reason I had formatted it as APFS. It's supposed to be Mac OS Extended. But a basic erase didn't fix it - had to do the security erase where it wrote over the entire data a few times. This fixed it!