blank page, with creases (about the middle of page), before it prints the intended page

HP LaserJet 4200 Printer

Keeps outputting a blank page, with creases in the paper (about the middle of page), before it prints the intended page.

This happens at random, but quite often. We have been using this printer for years without any issues. This has been happening for about the last few weeks. 

Any idea ?

thanks !