We're using HP CLJ 5550. Recently, when printing commands are sent to this printer, its producing loud crackling sounds, constant paper jams and black spots/streaks in the center of the paper (A4, Custom etc.). Image Transfer Kit and Fuser Kit is nearing their end of life so I replaced them with new. The first two errors were solved when the replacements are done. 'Til now, the third error is bugging me, tried to replace all cartridges but still no success. Any recommendations please, tried HP CS but no success. Saranghae TechSpot!