I do not wish to sound or imply being critical. For the ones like yours that come back to life by resoldering I really think that is great. I would live with that result willingly myself. My thrust is for the ones that do not and the guy gives up in disgust. Or lives with partial cruise control function. Not perhaps realising there is a second approach. But to be fair and keep it cost effective you would have to have access to an electronic parts outlet to get fair prices. Radio shack would be too expensive in my opinion. The list of parts is long. Perhaps a dozen or so. One known problem was that a certain type of capacitor was used in production that had an unusual high failure rate on these modules. Also some of the earlier transistors were garbage to put it mildly. I have seen many transistor junctions that were heat sensitive for example. I imagine the termination of the lead in the internal construction of the transistor was not really good in design or manufacture. . External heat running up the lead may restore the connection for a period of time in some cases. . This is why I am a little curious how long an average resolder job lasts. If of fairly short duration say six months then we know where to look next for example. If it lasts for years it was probably just a bad solder connection. Your problem was thermal for example and you are right it could be a poor solder or called in the trade cold joint that opened up when it shrank with lower temperatures. Perfectly understandable.