I'm doing the solder joint test on all SDS100s that cross my bench now. I'm working on fabricating some tooling so I can desolder the connectors and position them correctly when resoldering them. The problem is that they aren't seating all the way to the circuit board, and there are gaps between the connector pins and PCB pads that aren't being completely filled with solder. The pins are just touching the tops of the beads of solder instead of being immersed, and the mechanical weakness of the joint allows vibration, expansion, and contraction to break it. Once the joint breaks, oxidation sets in and interrupts continuity.