In my own case, TM lost the ability to make new backups to an USB-connected HD. It doesn't report errors. It doesn't explain. Trying to find something useful in Console is a PITA. The only visible symptom is that a few minutes after each backup starts, it ends without copying all that it promised at the start of the process.
I suspect the root cause is some 3rd party software interaction. But since the 3rd party software I have is installed and required by my employer, it's hard to do an A/B comparison.
I suspect the root cause is some 3rd party software interaction. But since the 3rd party software I have is installed and required by my employer, it's hard to do an A/B comparison.