Getting a line lead to trail only when copying off the platen. It starts from lead edge about 3" from the top and fades out 2" across the page(11X8.5) Also get smudging at lead edge of page when copying the Mita B&W chart. Cleaned all the mirrors and lamp but still there. Doesn't show up when using DP or printing. This one is an hour out so I could use some suggestions before going onsite again.
Glass not level maybe?

On canons we would get a similar symptom you described. The scan ribbon cable would get in the image path (mirrors) when the scan was made causing a line that would fade away.

I have also seen the scan ribbon on a falcon 2 get in the way of the scan path and cause a shadow. If it is only off the platen then that is a good place to start looking.

Manged to work on this for all of 10 minutes and appears I found a fix. Adjusted the #1 mirror upward in it's frame and removed and reseated the ISU cover and the line went away. Customers were in the middle of a big project so I had no time to verify which of these things fixed it. Probably the mirror.