UrBackup Windows wrong volume

Hi all, I just started using UrBackup to backup my windows machine to my nas and I noticed that the wrong Volume gets copied.
I have two drives installed: C: (500GB) and D: (3Tb). I want to backup the system partition C:

I used the default settings in the client (backing up the system partition).
And on the client the correct volume is displayed ©.

But on the server I am seeing the wrong volume (D)

On the filesystem at the Nas there is also the wrong drive letter.

Do you know where this could come from?
On my windows machine the disk 0 is D: and disk 1 is C, could that be the issue?