Hey Keith - A number of the solder joints have a crystalline appearance and may be cold joints -- see particularly the center third of the board, and some on the 8-pin socket. The shielded red and black pair and the resistor terminations on the socket look like they need to be crimped and resoldered.
Rather than trying to guess which one is the culprit, I'd just reheat all of them and only be satisfied when the resulting joint is smooth. Determining this on small joints can be a challenge. I use magnifier glasses to see what I'm doing, and can't/won't solder without them.
cheers and good luck, Derek
