My Scanner Is Strange

Epson and my repair guy are scratching their heads trying to figure out what is wrong with my scanner. The repair guy sticks a clear plastic sheet with black writing on the scanner bed and it scans ok but when he inserts my color negative it scans really dark and has those lines running through it. All of this using Epson Scan 2.76A which is the latest and greatest. So now he's going to replace the logic board and we'll see.