For some reason, I decided to try the self test — I DID use it when I first got the watch, and well, I have had it for a month.
Got "FAIL" every time.
So I called tech support today and while I'm on the phone … you guessed it … got a PASS both tries.
I figured they would say hang onto it, but they said we'll send you another one anyway. So it's on the way.