Dell V525w Scanner sticks when scanning

Hi all. My issue is NOT software related, I think it is a physical problem. When I scan a document the scanner sometimes makes a groaning, or shuttering sound towards the end of the scan job. At times it has hung up and stopped scanning, making a loud clicking sound over and over for several moments. The screen on the unit shows it is still scanning, but it's not. Makes me think it is hanging up on one or both of it;s guide rails?? Never had this problem, anybody have any ideas?? thanks Dave