So we're back in Mexico (for a while now) and I tore apart the light the other day. After swapping in the new bulb it was obviously something else. The switch seemed obvious since there was power to it. Shorting around the switch lit up the light, so being on a remote beach in Baja I tore the switch apart and jimmied things around, jammed a piece of plastic inside it and now it seems to work. For now.
I'm sure I'll end up replacing it, or bypassing the switch entirely. It would be nice to move it inside. Does anyone know where I can get switches like the ones FWC used in the panel near door, just above the floor? We don't have many options so we're only using one of the four places. I'd love to wire some other things into switches, and it would be nice to match the existing ones.