toshiba e-studio 2100c.

[just a tech]

having an issue with copy quality. getting a very light shading of color only on 2nd. side of duplexed copies. happens on prints and copies. if ya look very close, ya can see traces of all colors in the shading but magenta is the most prevalent giving the copies a light pinkish tone (on 2nd side) . now the real kicker is that all this is happening during black copying as well as color copying (light magenta coloring and all) . customer is gonna get their power for outlet rerun so they have better power. i have checked their outlet and they have reversed polarity along with a 9% voltage drop during a 20 amp. load.. now i know that undervoltage can cause some really weird shit but not totally sure that's what the whole problem is. anyone ever seen anything like this one before? any suggestions is always appreciated..