My Fenix 5 freezes shortly after I disconnect it from my Mac 10.12.4 Sierra. Necessitates a reset (hold light down for 25 seconds, then for one second after the shutdown).
30 second video here.
If I reattach the watch to the Mac while in this state, the Mac recognizes it, the time is updated, and it's back to normal. Until I disconnect it again, with the same freezing results.