servers i know nothing about, but HP printers i know lots about !!
51.2x is a laser error, it could be the laser is off centre, low output from the laser, but its most likely a dust buildup on one of the mirrors or lenses in the laser scanner assembly that simply needs cleaning off,
open it up and give it a good clean with a clean paintbrush and then try it again, if that doesnt help, try reseating the cables to the laser scanner, if that doesnt work, then its time to replace the laser scanner assembly i'm afraid
just for your information, 51.1x is a beam detect error