Lines on scans and copies are quite a nuisance. They can appear from time to time and then disappear or get thicker and more numerous.
If these lines appear just on scans and copies then they can taken care of without any maintenance or parts.
On most scanners there is a large glass bed.
To the left of the glass bed is a strip of glass. This strip of glass is involved when ever you do a scan through the feeder.
The paper slides past this small strip of glass. When there is even a finger print, smudge or small particle stuck to the surface of this glass, then it could cause a streak or line across the scan/copy. Any larger piece of dirt will definitely leave a line
Try removing this dirt and do a test. If you successfully removed it then the lines should disappear. It is easier to see the finer dirt with a bright light. Also most glass cleaners like Windex can be helpful.