Corrupted Time machine smartbundles
I've run into this problem a few times in the past and it just happened again.
On my new MB Air (bought just before Christmas) I got a message saying that it had been unable to backup to my NAS for over 10 days because it could not connect to the disk. Backups to an external drive over USB have been working fine.
I noticed in the folder on my NAS where all three of the Macs in the house (my Air, my wife's Air and my iMac) store the sparsebundles that there was a sprasebundle dated 12/23/2022 for my Air and a second one dated 2/23/2023 in the folder's recycle subfolder. The other machines show recent backups completed.
I also checked the NAS system log and it noted a "system event" five days ago which would be after the last successful backup to the NAS. No other errors were in the log.
Time Machine continued to claim it could not connect to the disk. I manually mounted the folder to the desktpop, this often clears such errors. This time it did not. I restarted the Air, restarted the NAS and still nothing.
I am now starting a brand new full backup from scratch, luckily I don't have much on the Air's SSD so the progress bar shows it will take another three hours.
I've been using Time Machine for backups for many years, formerly to a Time Capsule that I retired two and a half years ago repalced by my Synology NAS which Ialso use as a media streamer. I know there have numerous cases where users have found Time Machine backups over a network can fail. I'm just curious if anyone has ever found a way to recover other than simply trashing the smartbundle and starting a fresh backup.
MacBook Air M1 2020 1TB SSD, 16GB RAM
Mac OS 12.6.3 (Monterey)
Synology DS220j NAS (16TB, SHR RAID)
MacBook Air (M1, 2020)