One of my clients backs up everything all the time?

I have a quick question, as I’ve clearly missed something somewhere.
I have set up a new URBackup server (as a VM pointing to a big NAS with an NFS share for URB).
I have two clients, both Windows Server 2008 R2 machines doing image and file backups.
Everything works great, the images are fine, and file backups are fine.
The only issue is the smaller server seems to back up ALL of its 8GB of files in every incremental backup, while the bigger server backs up from 200K to 3GB in each incremental (out of around 200GB of files) as I’d expect it to.
I’ve looked at the settings and everything looks as it should, just the file paths are different.
I can’t see anything on the servers that is different. So I’m a bit lost and the space on the NAS is being used up very fast.

Has anyone else had this issue? Or have any clues as to what to look at or fix?

Many thanks!