Lines/Smudge on print

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Hi, can anybody help me with this. I'm having this cyan like lines on the printout. When I make a print on Single Color, it only appears on magenta and cyan, in yellow and Black, its clean, it is not there. I replaced the drum and magenta drum already, still the same. I'm thinking this is now something to do with the laser unit. Can anybody give me their ideas also?

Thanks much...