Mr Bulp,
I'm sorry to hear of your water ingress issues. I took my MP4 and BAC display through pretty heavy winter rains, everyday this winter and I was VERY pleasantly surprised that both the MP4 controller, the BAC display, the switch gear and connectors all went through it all without a hitch, and I have to say I wasn't at all confident they wouldn't be ruined on the first shower. But I was proven wrong. So I think you may have hit the quality control issues at GM on yet another instance (for me its PAS not working, BAC under reading etc etc). Hopefully you can get it sorted.
Good Luck,
WestOz