RE: Confusing crash probably Futaba RX related
How many cells are in your RX pack? 4 or 5? What voltage were you reading? Saying that there was "plenty left" means very little.
On the heat related lock outs that have been reported none have recovered as quickly as yours appears to have done so I doubt it is a heat issue.
Looking at your photo of the installation I would re-position one of the antennas into a vertical orientation in your fuse. As they are arranged now while being 90 degrees to each other they are both flat with respect to the surface where you are standing. That is a less than optimal orientation to maintain a link with the TX. The idea with the 90 degrees is to maximize the chances that one of the 2 antennas can be seen by the TX antenna. The way you have them I can see how they might have been blocked by the battery while in the Immelman.