Time Machine Back Up to Synology NAS

This is both a question and answer. I recently spent a few nights trying to back my M1 MacBook Pro / Monterey to my Synology NAS. The issue of Time Machine just randomly stopping back ups with no warning or clues is something I’ve experienced for well over 5 years using both local drives and NAS drives and various OS versions. It’s incredible a major feature of MacOS is this flakey. Calls to Apple have ranged from disinterest to open confusion.

Anyway, if you’re having this issue on NAS drives and specially Synology drives, what cured it for me was ensuring that AFP is the preferred protocol for file sharing on the NAS. When SMB was selected it failed everytime.

That option can be found on the drives DSM software at CONTROL PANEL > FILE SERVICES