There have been many inadvertent 76 float deployments, probably hundreds over the years. Usually on the deck after one pilot exits with the float switch still on. Many operators failed to install the STC float guard and fumbling on exit, or even getting the cyclic trim PB mixed up with the pop button set them off. Easy to do if you're stupid or tired. If the 139 system works as advertised, you should never have to manually activate the float switch.