Time Machine Error After Installing 11.5.1

Anyone seeing unusual Time Machine errors after installing the most recent OS update (11.5.1)?

I have an M1 Mac Mini and an M1 Macbook Air with Time Machine running on both computers. Both worked fine until I installed the recent update and now I am getting the same error on both computers: Time Machine couldn’t back up to “Time Machine.”

It appears to be a write error. I can read from the disks, but can’t write to them. I can write to other external drives, just not Time Machine.

Tried the usual reboot, etc, no luck.

Just curious if anyone else is seeing something similar?

I tried manual backup after reading this post, and it’s a success. My backup usually grow from 300MB to 10GB after OS updates. Try checking whether you have more than 10GB space left for your “Time Machine” volume.

I’ve never encounter an error log, but maybe you can try using Howard Oakley’s tool The Time Machine Mechanic (T2M2) and inspect on any weird logs

I had something like this occur on my M1 Mac mini, but it was with an earlier dot release of Big Sur. The volume was readable but Time Machine wouldn’t write to it. I attempted to repair the volume using Disk Utility and it couldn’t save it. I was having other issues where the drive would randomly uncounted, but that turned out to be the cable. Wondering if that might have had something to do with the corruption. Ultimately I just ended up having to reformat the drive and start over. Did you try First Aid with Disk Utility by chance?