Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
If paper goes into the unit before it stops, then there may be a sensor switch that is not registering any more, probably in the vicinity of the place where the leading edge of the paper that goes in, stops.
Examine that area carefully, with light, or a mirror if it's hard to see. Let me know what you find. (But don't apply direct light to the interior of the printer for too long. Laser printers' 'drums' can be damaged by too much direct/bright light. For longer than like 1/2 minute per 1/2 hour.)