Look at the Control Strip and Format Guide and make sure you have selected the correct control strip.
Then blow some air through the opening where the paper is inserted. (this is for possible dust build up)
The next step is to calibrate with a current calibration strip. The calibration strip should be less than 18 months old.
Go from the main menu, then to the channel that they are having problems with (Paper, Film).
See what heading is displayed under the channel they are using. If the heading is correct.
Check the date on the calibration strip. Is it newer then 18 months?
If the date is unknown hold the calibration strip next to the paper control strip, which apppears more white??? (the cal strip should be more white then the paper, or not yellowed in comparison) If the Cal strip is yellowed, then that might be the cause of the problem.
Check the lead of the control strip. Is it at least 1 and 1/4 inch or more from the leading eadge to the begining of the first target?
If these all check out OK, then check lamp and motor speed. If problems continue then have it come in for service.