ADVANCE C9075 PRO - problems with the magenta (Drum Unit)

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the magenta color test 5 goes bad (see picture)

IMG-20151019-WA0000.jpg

I had changed the drum unit, but the continuing problem. Then replace the drum unit with the yellow drum unit and also I change high card. The problem disappeared in magenta, but after a time returned to appear

Could you help me?

thanks