Duplicate backups from one Mac client to a Windows server

Hi,

I have a new server install on Windows.
My first test client is a Mac. It has two active network nodes (ethernet & wireless).

I don’t know if the two nodes are to blame but I have two backups running concurrently.
All the same files are being transmitted but the two backups have different names.
For example: Backup #1 is called “MyComputer.local” and Backup #2 is called “mc.domain.com”.

Is there a way to combine these or prevent duplicates like this?

A work-around could be explicitely setting the computername to one of the names. The hostname propably changes during boot or something.