Just for fun-

I've "repaired" a number of PCB mounted components over the years by doing exactly the same thing-just re-heating and re-distributing solder on apparently OK solder joints. There are a number of causes, but according to a former co-worker (SSB-Smart Summa Bi&ch), it's an oxide buildup on the cicuit board lands if they sit too long before assembly. If the manufacturer has a whole bunch of these boards made, then they solder them up piecemeal over the next 5 years, the ones soldered last have a higher failure rate than the ones used first. The solder looks as though it flows just fine, but has a poor mechanical bond with the silver on the board. Works for a while, but after some high-vibration use it breaks loose on a very micro scale and-problems start.

If I find this problem on my car, this is the first fix I'll try!