It all starts fine, but after a while (and this varies), the device freezes. I see the activity screen, but the timer and other metrics don't run anymore. I can only get the watch to work again by pressing the on/off button for a long time (powering off and on again), and sometimes that even doesn't work, and it need to be hooked to a computer.
It always forgets the activity I did while freezing/crashing.
Any thoughts?