Hi Daniel,
I'm not sure if you have resolved your issue or not but if you haven't I would recommend sending an email to
techsupport@rossvideo.com. This will insure that a ticket is created and your issue is investigated.
Out of curiosity, what version and build of XPression are you running? Can you take a screen cap of your hardware setup page with the Tile Mapper framebuffer?
#XPression