Hi,
There is a known problem that look pretty much like yours. This can happen when the 'preset document size' is wrongly detected from the platen glass.
Make sure your software version is 15.003.033.000 and newer and then you will need to activate a special code in tools to correct the problem. Here's how once you are at the correct version:
Log in as admin
Machine Status button
Tools tab
General Interface - General - SF0
Scroll down to #21 and select it - enable it - save it
Exit - Logout
Reboot
If it this too tecnical for you, do not hesitate to call Helpdesk and ask for a Tech to go onsite.
If you still have the problem after this procedure, there could be a problem with the scan carriage and you will need to call for a Service Rep to go onsite to correct or investigate further.
Hope you Success!
K.