Recently purchased a pre owned 2014 Epi es339 online(humbucker not p90). I plugged it in and worked all the controls and switches and determined that the tone control for the neck p/u was getting stuck in the high position even when trimming rolling back and forth. I sprayed it with cleaner and it became operable. A day or so later I plugged it in and worked the tone control and it was back to getting stuck in the high setting even when rolling back to lower tone. Any idea what may be the problem?