Well, let's break down what we know.
We know there are two, independent signals sent between the RC and the P3, since one can drop out and the other can be fine, and the app gives two different readouts. As such, the two antenna must transmit on two different frequencies, otherwise they would simply strongly interfere with eachother to the point where the entire signal would simply be cancelled out by the other antenna. It also makes sense to split the video and control signals over two frequencies, since the video is such high bandwidth.
IIRC the video is transmitted over 5.8GHz (because this is more susceptible to being reflected by buildings, ground, objects, etc.) and the control signal over 2.4GHz (again, less susceptible than 5.8GHz to reflection, which explains why your video signal drops out while your RC happily remains connected)