Digital BW, The Print

An acquaintance of mine has a 1270 & 1280, both of which have 
developed very slight banding in the direction of print head travel. 
It is visible only at viewing distances of 12" or less, but is 
nonetheless troubling. I would guess it is related to the paper 
feed, since repeated head cleaning and nozzle checks showed 
nothing amiss. Is this common? Is there a fix short of sending 
the printers in for very expensive refurbishing? Feedback would 
be much appreciated.

Jacques