Well dang, I've noticed a small number of times if I close the keyboard when the screen is on or off and then open it again, sometimes it does nothing when I open the keyboard and press a key. I sometimes have to press the power button once for it to come back on. I have not spotted a pattern yet due to not really looking out for a pattern yet. I'll see if I can replicate it and post back here. The Hello face recognition login worked fine every single time though.
My surface pro 4 has also been very unreliable. I removed windows hello, restarted then reconfigured it. I'm hoping this fixes it. This machine is by far my all time favorite device but OMG I thank god I'm no longer a student nor use this for work!!