Copy issue with Workcentre 4250 - half print from flatbed

Hello,

I need help with our xerox workcentre 4250 

When copying an 8.5 x 11 documents using the flatbed/glass the document comes out half printed on paper

Sometimes it works fine, sometimes it will print one half copied sheet & if you hit print again it  will be fine & sometimes it will only print half copird sheets.

We have used this printer for awhile with no issues. this just started a couple of weeks ago. 

I have reset the printer several times, sometimes it helps , sometimes it doesn't

Any suggestions?

THANK YOU!