Recent Time Machine Backup Failure

Hi:

Time Machine has just (for about 1 week) started exhibiting some wonky behavior that my old brain can’t figure out.

For years, with an identical hardware setup, TM has worked flawlessly.

Then a week ago it started giving me an error message regarding a .dmg file that it previously copied no problem.

I went online searching for an answer and rebooted my machine, ran Disk First Aid on the Time Machine dedicated external spinning hard drive (no errors), and ejected and remounted the Time Machine drive.

All this did was swap the impacted not backed up file error from one 3 GB .dmg file to a different 15 GB .dmg file.

The error message is: “1.jpg”

The System Settings for Time Machine say: “2.jpg”

The Time Machine drive has plenty of space on it: “3.jpg”

System info is: “4.jpg”

(Just a theory, but could all of this have started with the latest Sequoia update???)

I’m stuck. Any suggestions would be greatly appreciated!

Thank you.