I have had my 66i for just over a month and just had it on a month long backpack. I have noticed several times that it decides for some reason to turn off tracking. This means that I need to check it as often as I can to ensure that it is still tracking (sending coordinates via satellite to people watching my activity). This happens perhaps once a day -- sometimes after only an hour or so, sometimes after 4 or 5 hours. I haven't identified any pattern. Is this a well known problem or bug or anything others experience?