Dark line on end of drum cartridge..

[W_W]

Dark lines on end of fuser on all the color drum cartridges.  That was why I changed them out in the first place, 

but now they are doing it again?????

[rdaniels2]

On first thought, I was thinking that it might be something with the transfer belt.

The black lines, are they just black toner lines or actual groves ?

[W_W]

On of the users has a Workcentre 6515 DN network printer that was printing dark line on left side of page.  I changed out all the color drum cartridge, because they all had a line on the fuser roller, but now it is doing the same thing.  I checked the new cartridges and the line is on the new ones now, what could be causing this.  I have checked the rollers but cannot find any damage.

Thank you,

Woody