MT mapping warning in Disk Utility

In preparation for updating my 27” iMac from Big Sur 11.6 to the latest macOS Big Sur 11.6.2, I used Disk Utility to check my fusion drive. I found the following warning on my “Container 2” device:
Disk Utility warning.pdf (218.7 KB)

I reran Disk Utility several times on “Container 2” and this one warning remains.

Does anyone know if this is something to be concerned about? (The “Macintosh HD - Data” and “Macintosh HD” devices have no errors).

Generally speaking, you should never be “concerned” about warnings when DU tells you the disk is “OK”. That said, I have no idea what that warning means and have never seen it reported by anybody before.

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Glad to hear that. A few days ago, I got the following (edited) report from Disk Utility when I asked it run First Aid. (I wasn’t so worried that I ran to TidBITS to ask about it, but I was worried enough to save the transcript.)

Running First Aid on [startup volume] (disk3s5)
warning: container has been mounted by APFS version 1933.41.2, which is newer than 1677.141.2
warning: disabling overallocation repairs by default; use -o to override
The volume /dev/rdisk3s5 appears to be OK.
File system check exit code is 0.
Restoring the original state found as mounted.

Operation successful.

Any comment? Could this be related to the Mac’s inability to complete a Time Machine backup?

You’ll have to ask Apple.