I am using S7 Edge (Samsung)

It was working very well for the first month. Some how not sure why, suddenly, every time I started flying, its fine for the first 10 minutes, then the video will get distorted even though its  flying just right next to me. Thus, this situation causes me not having the Live Video Feed.

My question is, is this relating to any issues or just purely due to my phone? I cant figure it out. It was working well previously.

some facts:- its the same phone that fly well for a month
- the phone got a firmware upgrade.
- it was flying well every time for the first 10 minutes after the phone firmware upgrade
- i tried to use another phone which is android version 4.4.2, but cant get a Live video feed at all, thus cant try on another phone. (please advice how to fix this as well. Thanks)

The easiest way to find out is to use another phone. the Android 4.2 phone is probably not enough in specs.   

I tend to believe it's the drone's transmission chip that's overheating though.  In this case, you need to send it in to add some cooling paste over the chip.