The issue where you do not regain FPV after losing it happens due to a problem with the DJI code.
The video reconnection process is handled by the SDK but sometimes, for some reason, it does not reconnect. In my case the only times I've seen it not reconnect is when I go out of range. I am not quite sure why you are losing FPV when the Phantom is close to you though. There is no debug mode for this due to most of that code being in the SDK. To be honest, it's something I've been wanting to fix for a while, but at the same time it needs to be fixed by DJI really (we can't access the code and just reproducing it in my case is not easy since I have to go out of range and hope it won't reconnect, because sometimes it does actually reconnect).