Hi there,
Are you running WinPE 32 or 64 bit?
Also, do you have any patch installed post-SP2?
I would start making sure you have the latest component patch available from here:
LDMS 9.5 Sustaining Patch Information
In the list of the updates I see the following:
Provisioning - MaptoPreferredHandler_x64.exe doesn't map preferred server on WinPE 64bits
Maybe this is the issue you are facing?
As a workaround you can manually map a drive directly pointing to the preferred server and then deploy the image from the network drive, if this is suitable to your environment.
Hope this helps
Francesco