I've had two Majestouch 1s do this.
One of them had a switch that wasn't snapped into the plate properly before soldering, and it was supported only by the solder joint, which started to come apart. This was a known manufacturing fault that was resolved with the Majestouch 2. The switch itself could be pressed down a millimetre or so, and then snapped into place properly and died. It needed re-soldering.
The other one, the switch just needed some WD40, apparently.