Backup & Recovery 16 - Data block information was not found in index file

I have been backing up my PC to my NAS drive on my home network and then creating weekly increments since Backup & Recovery 16 first became available. Once a month, I delete the backup and increments and re-run the full backup again.

Several weeks ago, I started getting an error when I tried to create an increment (see screenshot below) and I have tried everything I can think of to resolve it, without success.

Attachment 390

Last week for instance, I ran chkdsk on both drives to be backed up and no errors were found. Once the backup had finished I performed an integrity check of the archive, which completed successfully. I then tried creating an increment and got the same error as before. I tried again a few minutes ago and it still doesn't work.

What could be causing this error and how do I resolve it?