how to make the switch work again?

I have In Sink Erator 15 and though it still works fine the switch at the top seems to have a problem to turn itself off. I have been using it by turning it on and off by switching from the main switch at the back of the cabinet.
The switch in concern is the one that you turn R or L to make it on or off and it situates inside the sink.
Anybody else has the same problem?