Hi there, and welcome to the forums.
Here are some pieces of info for your question - one for possible causes, and the 2nd is for cleaning the printer to stop the jams. Good luck, and I hope it helps :)
http://h10025.www1.hp.com/ewfrf/wc/document?cc=us&dlc=en&docname=c03874521
Do not print on both sides of the following types of paper, or jams might occur:
Transparencies
Envelopes
Photo paper
Glossy paper
Paper lighter than 16 lb bond (60 g/m2 )
Paper heavier than 28 lb bond (105 g/m2 )
Several kinds of paper require a specific orientation when you print on both sides of a page. These include letterheads, preprinted paper, and paper with watermarks and pre-punched holes. The printer prints the first side of the paper first. Load the paper with top edge first and the print side down.
Paper Jam:
http://h10025.www1.hp.com/ewfrf/wc/document?cc=us&dlc=en&docname=c02915719&lc=en&product=4323659&tmp_track_link=ot_search