I'm having the same problem on Gear VR. I use a galaxy 7 edge. I used to play all the time without any problem, But picking it up again yesterday the audio was awful with or without headphones and I'd get an overheating warning before I finished a single game. Honestly unacceptable. It's frustrating the dev would release a patch that breaks the game like this.
There are many device-isolated variables that can cause performance issues considering the amount of computing power required to run VR. Have you downloaded any new applications since last playing the game? Maybe ones that operate in the background of your device? @Wa5t3dW1zard