That printer doesn't use a transfer belt, but instead uses individual OPC drums for each color (CMYK). DrB0b is right... changing the cartridge should resolve that issue. Looks like remanufactured cartridges may have been used, with substandard or worn out OPC drums.
Just my $.02
"What the captain doesn't realize is that we've secretly replaced his Dilithium Crystals with new Folger's Crystals."
--Greg