When trying to perform a printhead alignment on an HP Designjet 110plus nr, 120nr or 130nr printer (110+/120/130 printer with optional rollfeed) the media can jam when trying to read the print alignment.
During the printhead alignment paper is printed and then pulled back into the printer to do an alignment of the media. During the pulling of the printed sheet back into the printer, the paper jams on the cleanout assembly.
The media catches on the paper guides. In many cases, these media guides are misaligned (see below). 
Figure : Incorrect Position of Lower Media Guides
After removing the cleanout assembly, pulling away and down on lip, while pressing down on the media guide, the guide can be snapped back into correct position.
Figure : Adjusting the Media Guide into Correct Position
This is the correct position of the media guide. 
Figure : Media Guide in Correct Postion
