Phaser 6125- splotchy toner

Hello,

We had a user replace the yellow toner in the Phaser 6125 after which a document was sent but it where there should have been solid yellow areas the yellow was mixed in with cloudy white areas.  I ran some demo prints from the printer and they appeared fine.  But when another document was printed from a different computer the cloudy yellow area remained.

I asked the user to replace the yellow toner and she reported back that the problem was worse.  Again I printed a demo page from the printer and this time I noted that the cloudy yellow covered all white areas of the paper as well as the yellow areas.

I have since asked the user to purchase an Imaging Unit in an attempt to correct the problem. 

I am I following the correct path or is there something else that is the cause of this?

Thanks in advance.