Ok, no responses that's alright. From my investigation, the RCS relay board design is unreliable (details below). Does anyone know of another serial controlled relay board I can use.

Debug details-
Of 8 relay boards being driven from 1 power supply, I disconnected 6, to verfiy that there was not a power supply problem. The voltages stays right at 12 V and the current drain is fairly small even with all 8 boards powered (I'm using a 1.2A supply). The relays are turned on in sequence, not all at once, again to make sure there isn't a large current drain which is preventing 1 from latching. Still no dice. The stuck relay, which is not always the same one, shows an led which means it should be on, a tap on the relay will cause it to latch properly. I tried disconnecting the load, even though I didn't know how that could be causing the problem, it wasn't. I even tried applying a larger voltage to the board to try to get the relay to pick up, but to no avail. Final conclusion - the RCS relay board is unreliable.