laserwriter 12/640 PS

My old 12/640 stops pulling the paper into the machine. After starting a print job, the printer starts pulling the paper but stops about after two inches.

This happens no matter what cassette I use, even if I choose manual feed. When I open the printer I can see the end of the page about where the toner cassette is located. Please help. It`s an old workhorse and I want to keep it for another decade. 8-)