Joined: Sep 2009
Posts: 2,067
Likes: 73
From: USA
Bikes: 84 Pinarello Trevisio, 86 Guerciotti SLX, 96 Specialized Stumpjumper, 2010 Surly Cross Check, 88 Centurion Prestige, 73 Raleigh Sports, GT Force, Bridgestone MB4
If you take it apart you will see a tiny little push button down at the bottom. It must be contacting the outer housing and being pressed when you hit a hard bump. Perhaps gently bend the outer casing away and push the button mechanism up and away. J