Hi, Well I am unsure if you have the same issue I had but it was similar so maybe this will help.. I had similar issues and did tons of research and finally found one thread buried amongst the interwebs and he said he was having issues with tracking and the fix was to change the reflective tape on the track ir clip..
Once I found the correct reflective tape and put on the new tape it worked perfect like it did when it was new.. I found some of the correct tape at Walmart in the sporting section it is Tenacious Tape(TM) Reflective Tape.. here is a link:
Link to Tenacious Tape at Walmart..I am not sure this is your exact problem but I found after some time the original tape wears out and needs to be replaced..