^ They updated the build to incorporate the latest drivers from Intel for the Atom x7 SoC, I'm not sure which build MS did that with though.
Heat up by the back camera is normal, that's where the SoC is that operates your Surface 3 (the CPU, graphics, RAM controller chips, etc.). It's normal for that to heat up quite a bit if you are conducting heavy tasks like video encoding. It shouldn't get warm if you are just playing back videos, unless you use Chrome for online videos as that relies on software decoding instead of hardware decoding like the modern version of IE.
I have never had my Surface 3 (same model as yours) get hot but it does get pretty warm when I'm encoding videos with the display on. Having the display turn off helps with that. The batteries for the Surface 3 are all in the kickstand region so any warmth there signifies that something is going on with those and they really shouldn't get warm, not even when charging.