When I get home from a ride I press the Start/Stop button on my Edge 810 and then press Save, about 50% of the time I get the "Upload Failed" message (I then have to upload via USB).
I've always put this down to the poor mobile phone signal here, I was watching the phone to day and although the phone signal was poor (1bar) the WiFi was full strength.
Does anyone know if the Livetrack tries to sync over WiFi if it's available, or if it always uses the phone signal?