Mudbox map extraction adds border

Hey there,

I'm trying to extract a Ambient occlusion map in Mudbox, but always I do this, it adds a white and also a black border like in the image below.
This also happend on my hightmap too, but I was able to cut it off in World Machine.
I tried some different formats and settings and also searched the internet, but unfortunally without any positive resault.

Target- and Source Model have the same size. Mudbox is updated to SP3.

Thanks for any help

Dennis aka Talaris

What are your map extraction settings?