Anybody have any issues with the maxxum not wanting to go whne the foot switch is depressed at low speeds? Mine is just a little over 3 years old and has started doing this. Won't go in eith Mon or Cont when it happens. I can usually turn up the wick and fiddle with it a little and get it to go for a while but it will do it again. I can hear the switch "click" when depressed but nothing happens. Any thoughts???