Aparrently, these are susceptable ( did I spell that right? ) to water ingress.
my bikes one was damaged so I took it apart to see, you know, as boys do. And sure enough it was water stained on the pcb.
Confirmed by a guy at BMW.
Id suggest a bit of waterproofing to safeguard from this.
Athough, the lack of battery power thing could be true too, especially if the system is having a massive load applied suddenly.
Id go with the water thing though as they seem prone...
Good luck