Strange stuff there Vickers, the most common thing that I've seen that just shut's these down is the ignition switch going bad. Just don't want to see it happen at an "inconvenient" time. Mine went on a jack rabbit left across two lanes. It was happing at such inconsistent times that I forgot there was a problem and would always start right back up.
Maybe just for the heck of it open up the switches you got from the junkie and put the best looking one in. Then if the same thing happens you can start cracking wire looms.