Backups being deleted instead of being retained

I have backup jobs from different sites pushing to the backup server and it seems there is an issue with one of the sites and retaining backups. This site’s backups are checked every Monday and looking at it today there seems to be an issue.

The latest backup done on 4/6/2019 is an image-weekend backup and was ran successfully. This backup contains SYSVOL, C:, and D:.

Looking at the previous week’s backup. It only shows an available backup on the D: for 3/30. The week before shows a retained backup of only the D: again. On both of those backups there is no SYSVOL or C: backup. I checked my logs from when those backups were checked on time and URBackup did show those drives being backed up properly. But now those backups are not listed.

Prior to those previous weeks, the last backup set is from 07/29/19.

Any idea why some of these backups are only being retained partially? I need the entire backup to be retained.

Looking at my settings, they are correct. Minimal # of retained incremental image is 4, with a max of 30.

Any insight on to the missing retention of some of these backups?

Enabling server debug logging and then looking for why the image was deleted would help in finding the cause of this issue. See here for how to enable debug logging: Having problems with UrBackup? Please read before posting

Outside of that: Do you use image backups to VHD chains, and if yes, do you run a (synthetic) full often enough?