It doesn't? That's brilliant news! OK great, so if we keep it like so, we only need an external switch, which we already have anyway. This makes things much easier! Feels a little like being defeated, since we simply can't work out where our fault is and now we'll just bypass it anyway. Never mind. Also, it hadn't occurred to me, but as you say a BEC would kill all power to the RX when the link is out anyway.

OK, thanks again, I can't believe I almost didn't ask the question!