Update:
I feel like I've fought with this enough. Despite making the registry tweaks I previously linked to, I was still having big problems. In fact, I could easily reproduce the issue by doing the following (not sure which, if any, or all, of these steps are necessary
to reproduce) but here is just ONE of the scenarios that was happening to me, and I could reproduce it on-demand:
- First, I verified that my power settings for "Go to sleep" and "Turn off display" are all set to "NEVER" for both "A/C" and "Battery" power. Also verified that I had un-ticked the box for the "try to detect when I am away to save power". Also verified that
I had un-ticked the box in the Display settings for "automatically adjusting screen brightness."
- Lay in bed (in the dark) with my surface pro on battery power (nearly fully charged) with the new signature keyboard attached.
- Turn the brightness of the display all the way down (using the key on the keyboard).
- Start watching a movie or do anything that causes the contents on the screen to change (such as a movie that has scenes that are bright and then scenes that are dark.)
- If the scene in the movie goes to some scene that is "dark", then the light that is emanating from the screen will be less, and that will cause the surface pro to think that it is running in a "darker environment" and will begin adjusting the screen brightness
even darker automatically. This causes even less light to be let off by the screen, and it will adjust the screen brightness down even further. It's kind of hilarious to watch the thing fight with turning it's own brightness up and down based on the amount
of light that it-itself is giving off. If the scene in the movie stays dark for some period of time, it will keep auto-adjusting itself darker and darker and darker, until finally the the surface pro will put itself to sleep.
I was able to reproduce this last night time and time again. But this is only one of the scenarios I have encountered. There seem to be other triggers for it (that aren't related to the amount of ambient light in the room). However, the scenario I described
above is the only one that I am able to re-produce on demand.
One theory I have is: Maybe the surface pro is incorrectly thinking that the keyboard cover is being "closed" when it gets "dark enough" and is putting itself to sleep because of that.... Combined with the fact that the reason it is "dark" is because it is
turning down the screen brightness on it's own. This is only a theory--I don't know what mechanism the surface pro is using to detect whether it is closed/covered or open... but if it is using the camera/brightness, then this might make sense.
Anyway, I just got tired of it, and before I went to sleep last night, I decided to just wipe/system-restore the thing, and it is going back. Not going to pay over a grand for a device that
will continue to just shut itself off while I'm using it... and while Microsoft support folks were always nice to me when I contacted them, they haven't gotten back to me since last weekend.