DP9.06 - network share backup - incr backing up same data from previous night

I have a DP cell 9.06 which backs up a NAS share of veeam data off a D2D. The backup is just an incr so it should only be backing up one file a night which is the veeam backup file.

What we are seeing is that each incr is backing up everything since the full, not only whats been backed up since the last incr.

Anyone seen this behaviour. I would expect this from Incr1 but Incr should be since the last backup not the last full.

thanks!