Audio Systems: Sony turntable, sony turntable, sony ps

Question
I have a Sony PS-LX520 linear tracking turntable that will play just fine but then come to a spot on the record where it gets stuck, and it plays over and over.  When you lift the stylus off the record you cannot advance the arm to get beyond the spot without first moving it backwards. It seems to be a mechanical problem with the arm riding on the bar rather than with the stylus, as the sound is fine. I've mechanically advanced the tone arm back and forth with the controlls to see if this would help but it invariably will get stuck somewhere on every album. Any ideas as to what I could do before I bring it to be serviced.  

Answer
there should be a 'skating' fine adjustment somewhere near the pivot point (probably under the cover) that controls the amount of 'inward force' applied to maintain tracking in case of a skip. but my first thought would definately be to clean the tone arm pivoting mechanics before making any adjustments, a little dust in the wrong place will make it do just what it is doing....