backup – Greatest practices to debug macOS Time Machine errors?

My practices (greatest or in any other case):

1. Ignore all technical descriptions, discussions and options greater than about 2 years outdated. The internals of Time Machine (TM) have modified in two main methods:

• Previous TM used HFS+ formatted disks and avoids duplication of recordsdata used onerous hyperlinks. Something associated to this (like all three of your 12+ 12 months outdated hyperlinks) is ineffective at present.

• Present TM makes use of APFS formatted disks which makes use of “snapshots” for reliability and avoiding duplication of recordsdata in every backup. The internals of this have modified (e.g. checksuming of recordsdata) additional limiting applicability of say 4 12 months data.

2. TM to community hooked up drives (whether or not one other Mac or a NAS) are notoriously fragile. In instances like yours, utilizing a Synology NAS, all questions must make that clear what NAS is getting used in addition to having already ensured that the NAS explicitly helps TM and is appropriately configured.

3. Logging (and that is the crux of your query):
   Time Machine writes to the unified log – it doesn’t have a separate log. The unified log is voluminous (to say the least) and it’s troublesome to make any sense of it. However:

• Howard Oakley has written a variety of utilities to help. Time Machine Mechanic, Mints and Comfort are launched on this web page T2M2, and many others.

• Begin with The Time Machine Mechanic. Right here is when there was one profitable backup:

4. Learn and, hopefully, perceive the various posts concerning Time Machine in the direction of the tip of the above linked web page. Some depth of understanding how TM works is important to diagnosing points. Time Machine in Sonoma detection and analysis is straight related.

5. When utilizing TM to a different Mac I’ve at all times had bother and determined that pursuing the problems is wasted effort. I’ve turned to straight hooked up storage even when that’s solely intermittently linked – e.g. to a MacBook. YMMV – others do efficiently backup to Synology.