Exactly my experience. I've used TimeMachine with external USB drives, Apple's own TimeCapsule router (am I remembering that name correctly?), and various NASes. None of them could maintain a stable backup for a year. And you know, a backup that can't back up, isn't a backup.

I have since implemented a borg backup. This also failed at one point, but at least its five-year record remained readable, so no data was lost. Now I'm using restic.