Digital BW, The Print

Two questions: On my 1160 I notice that one (just one) of the pizza 
wheels is leaving tracks. Never happened before. Anyway, is there 
simple method for either removing one wheel or keeping it from 
touching the surface of the print? Second, and more important, I 
notice that my prints occasionally have dark lines (I sometimes see 
lines as strings of individual dots) randomly placed inside or 
outside of the print area. Does anyone know the cause of this 
problem? I recall someone having mentioned experience a similar 
problem, but I couldn't find a reference to it in the archives. Any 
help would be appreciated?

Chris Hargens