Sounds like a bad switch to me. Sometimes people have a few other keys on the bike ring, going down the road, keys jingle, vibration after a while loosens the contacts. I have had it happen about 1/2 a dozen times when riding, the keys would jiggle around and actually turn off ignition while I am riding ! So not a good thing to have happen, if one has their wits about them, they will suddenly know what the scoop is. just keep ignition and fork lock key on bike ring.