Just had a look at mine. At the button end a philips head screw holds down the sliding part of the switch with a washer. The head of the screw is round, and fits through the Y part of the switch as it is pushed in. Is the screw the right one, too long or the washer too thick? It is a tight fit (or you could call it precisely right) .At the other end there is a plastic mechanism that is flicked left and right, and when the button is pushed it turns off. Does that still work? I put some grease on mine while it was apart.
