I am having significant problems with my Edge 830 when recalculating a route. If I get off track it starts to recalculate but then the unit shuts off. I have to turn it back on with the power button but then I've lost my ride information completely and I have to load the course all over again. Also if I'm riding and I try to use the unit to return to start either by direct or retracing the route, it also shuts off. What can I do about this?