epson R220 Print To DVD Error

Epson R220 printer that is giving me problems when I try to print using the CD/DVD tray. The tray loads into the printer fine (no slippage experienced by others) and I have plenty of room behind the printer (trays not hitting the wall or anything). However every time I try to print I get the "CD/DVD Tray Not Set Correctly" error and the printer ejects the tray back out. Printing to regular paper works fine, I only get the error when using the DVD tray. Anyone know how to fix this? I read elsewhere that it could be a dirty sensor but I cant seem to find where the sensor is at. Any help fixing this problem would be much appreciated!!