To me this is a support ticket and possibly posting on the forums - https://forums.veeam.com

Not sure what else to check other than maybe the Veeam logs here - C:\ProgramData\Veeam\Backup

Our customer support team takes care of such issues. Unfortunately we (product management) cannot fix technical issues over a forum topic. Our customer support team is equipped with the tools and the right training to analyze log file packages from our products. Log files will tell us what the cause of this issue is.

For me this looks like a database issue. Either a support technician can fix it, or the database must be reseted to zero. Which means job configuration and other settings will be lost.

I would definitely wait for our support engineers to provide a solution after analyzing the logs.

Best,

Fabian