So I finally solved the problem of my phone randomly shutting off. For those of you with a Hyperion TPU Case (the case specifically made for the 4200 mah batteries), make sure you cut out a hole for the power button. I found out that the case was pressing against the power button and shutting the phone off.
I verified this myself by taking the case off, holding the power button in, and sure enough, after about 10-15 seconds, the phone shuts off. Cut the power button out of the case, and the problem hasn't returned.
I verified this myself by taking the case off, holding the power button in, and sure enough, after about 10-15 seconds, the phone shuts off. Cut the power button out of the case, and the problem hasn't returned.