As I've been messing around with Ham Radio for some time now....If you think it's a thermal problem (when it gets hot) you can pinpoint items with circut board freeze spray or something like it. It will allow you to almost make parts "fail at will" if the parts problems are heat related. I've even made makeshift cold rooms and hit them with a tank of Co2 to prove out the problems. In a pinch a zip-loc with ice may get you by. OM