HPLJ M402dn duplex jam - possible resolution

[Guido257]

Open rear door. There is at the top a gate which pivots horizontally a few degrees. It directs a sheet of paper either into the output bin or back thru the main cartridge to print a second side. It appears to stick ever so slightly against a rubber bumper on the left side when pulled out. Before a print job, I pull the gate so that it hangs vertically away from any travel limits. I have only tried this about a dozen times, but, thus far, no jams.

[Repairatrooper]

Often soft foam is used as a buffer to reduce noise. Often this foam degrades over time due to exposure to ozone and heat from printer. This is quite common on the metal solenoids in the pickup assembly but I have seen it happen on exit assemblies as well. If this is a simply plastic part you can safely just clean off the sticky residue and use the printer as is. With metal solenoids it is necessary to insert a replacement buffer or the solenoid plate will eventually become magnetized and start sticking again.