It could be that some tiny conductive crud has shorted out a component - the spacing between surface mount IC pins is so small that a piece of metal the size of a grain of sand will do it. What I now do is coat the receiver PCB with 5 minute epoxy to insulate and shock protect all the components. Just spread a thin layer on with a matchstick and avoid the connectors. I haven't had a receiver die in 5 years since trying this.