Exchange 2013 backups complete with status code 0 on Netbackup however last backup time stamp on exchange doesn't update

update:

Support suggested to create a new policy and try the backup. So I created a new policy and  tested the backup for a few databases, backup worked fine and exchange updated the backup time stamp. I also tested by copying the old policy into a new one, that too worked (surprisingly). Anyways things worked for a week however the problem is back after this weekend's backup. I'll reopen the suport case though  I have a feeling this might not be a netbackup issue.

Funnily enough, my initial reaction is to lean the other way, and say that it does look like a NetBackup side issue, because a policy change on the NetBackup side does cause the 'dates' on the MS Exchange side to be updated... which makes it look as if it is NetBackup code which requests the "date to be updated" on the Exchange side.   A support case is best, because sometimes, as in this case, it's not probably not easy for us as admins to determine where the true root cause actually resides... you kind of need access to the source code to identify exactly where the call is taking place and what the related log messages would be.

Thanks @sdo, I'll post an update when  I have one. I have been googling what exactly is the significance of the backup time stamp on exchange without much luck yet. I mean is there any exchange tasks that cannot run till the backup time stamp update on exchange side and more importantly does it render the successful backup in Netbackup useless for a restore since exchange doesnt know it was backed up.

I know this is not an exchange forum however it would be great if someone knows about this, please comment.Thank you.