Most likely the pickup braids are not making good contact with the track rails, either because they are dirty or because they need to be adjusted. Try cleaning the braids with alcohol or lighter fluid. WD-40 is not a great lubricant because it is mostly solvents with a rather small amount of oil. If the WD-40 is in the usual spray can only a fraction of it will get where you need it to go, the rest will just make a mess. Only use lubricants that are plastic safe and put those in container with a needle tip.