I had that issue with the Spot 2 - it didn't send OK messages for the last three days of a trip. However I'm thinking it was more likely user error. I had a few trips under my belt with the Spot 2 and became complacent, on the 'failed' trip I would click the OK message and wander back and switch it off without checking to see how long it had been on for. Spot recommend transmitting for at least 20 mins to make sure the message goes through. So I'm thinking I didn't leave it on for long enough... In subsequent trips I have left it on for a good period of time and it hasn't failed once, even under thick forest.
And yes the point Franco bought up came to pass. The emergency contacts became worried about no 'OK' messages and contacted the Police. There was no search and rescue mounted as the Police advised to wait until we were due to walk out before sending out the cavalry. I had no phone signal until I was out of the walk, when I got a text to say the police had been contacted... At first I thought this was a joke...
The other interesting point to come out of this was jurisdiction. The walk was the northern end of the Aust Alps and crossed the NSW and ACT border, apparently the Police were trying to pass the ball as to who was responsible for following up - where the signal was last lost (NSW) or where the party was suppose to walk out (ACT). Luckily, this didn't have to be resolved
