The author posted a fix, but how do I check if there is a problem in the first place?

Hi! OP here. In my case Time Machine stopped doing backups to the server, period, and would keep silently refusing to do so. I encourage you to check backups are happening.

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ndegruchy 6 hours ago | parent | prev | next [-]

I would try to do some restores of random files. Kind of a "canary in the coal mine" test. If you have problems with restoring some files or folders, then you'll have a problem with doing larger restores.

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_rs 6 hours ago | parent | prev [-]

I agree - I am running my own Samba server and I don't think I'm affected, but it isn't really clear to me how to double check or why Apple's new default broke things in the first place

	▲	jcynix 3 hours ago \| parent [-]
		You could create a timestamp file on your Mac, where your Mac adds a timestamp per day or hour and have a script check that the timestamps appear in your backup.