Clean the track, clean the wheels, clean and lubricate the pickup.
I've successfully used the following (but there are many other opinions/experiences to be found)
- GooGone on a rag for wiping down track and wheel cleaning
- Labelle 102/107 or Mobile 1 Synthetic 5W-30 for lubrication
- CRC 2-26 for cleaning and lubricating the pickup roller itself
- Labelle 106 or Red N Tacky #2 for greasing gearboxes (not applicable to y our inquiry)