Back from the dead.
I picked up some of these 'warrantied lights' recently It's certainly NOT the connection. However, if it were the connection, a bit of dielectric grease on the contacts will prevent the corrosion.
I'll play with them a bit more at work, I suspect they have a bad solder joint. I'll re-touch the joints at the connectors between boards and see if it helps. I can get them to all light up and flicker a bit if I put pressure on the solder joints.
The light came apart reasonably easy with a small screw driver. Sealing them back up will be a bit more of a chore, but not impossible. I'll get the big camera out to reassemble them after I repair the board.
Anyhow, took a light apart and this is the bench test:
