I have two machines , an A and B model. They work great and yes they do throw fits occasionally.
Dust collection is paramount!!!!!!!! My down time is almost 0 since i added them on mine.
I think there are instructions for removing and cleaning the rear roller somewhere.
Also possible head alignment issue. I check mine by just measuring from the same point on head to the drive belts on each side.
Im sure someone else will pipe in.....just my experience.
As stated before.... a good clean and lube may fix everything.
Brent
A,B machines, PE,probe,conforming vectors, centerline, 2d,3d,stl and dfx imprt, rotary , 3.xx, Pattern Sculptor
OS X Yosemite
Woodwork is what I do to pay for my tool addiction.