Concerning random crashes to the built in white digital face, or a system reset
--If you are experiencing similar crashes this info may be a starting point.
My watch face was crashing and I was finally able to get it reproducible. It would often crash when a message was received when it was in high power mode.
My watch face runtime memory usage was pretty high and I had a lot of global variables, I was also using some large dictionary variables. I suspect that the incoming message would force my program onto the stack and in high power mode the watch face would get called every second and the message would keep making my watch face get restacked and the memory would run out.
Reducing memory usage by converting the dict's to arrays solved the problem. My program had a freemem of about 10750 with the crash bug and 18000 with no more crashing.
I could be wrong about the reasoning, my dictionary (over)usage could have been the issue. But at least things are working now.