Hey yzer., you seem to have very good luck. We need to direct sigelei r&.d to this thread and the 1cent fix. Dropping it especially on the head can easily dislodge it, by the battery getting shocked into the positive pin.
One preventative fix I have seen is .. When its new put epoxy around the posi pin in the black disc and also around black disc to body. The disc slides right out the top it's sitting on a ledge. Just don't get any On the top contact part of the pin.
This is the only preventative mod you can do to it without taking apart, but again it's pretty easy. :$
Can you hand over a few links and info/worklog? I'd love to prevent my V5 button and internals from slipping.