Today it happened to me the second time. I was using my watch on a hike. Course navigation was turned on and after about 2-3 hours of recording, when I scrolled to the temperature datafield, the device got completely frozen. I had to do a soft reset to get it work again.
In fact, at the first time I was also experiencing extremely slow or even completely not responding navigation. I mean, the arrow that shows the current position didn't follow me on the map and after the first turn the watch didn't give me more instructions about turns. I think this behavior was also related to the TEMPE sensor because I didn't experience the same when I was not using my TEMPE sensor.
Have you seen similar problems with or without TEMPE sensor?