We are using the Map My Tracks api.
Sometimes when a request to start a new track is made the MapMyTracks incoming proxy server server responds with a message similar to - proxy error No response from upstream server (I haven’t recorded the exact message). We interpreted this as no track is started so waited a minute and then started a track again, however a track was in fact started so then there would be multiple tracks running simultaneously. To fix this we now start a track, ask for the current track data and don’t try and start another track until we get a message saying there is no current track.
The server should start a track and respond with the track ID or if its not going to respond not start a track. Looking just now I see lots of 0 length simultaneous tracks from axlrio, one of which is http://www.mapmytracks.com/explore/activity/my-wahoo-fitness-title14450/ . This is what our app did until we implemented the fix. axlrio is using the Fisica Fitness app so it looks like that app might be having the same problem we did.
We first saw this on thursday 8 December and have seen it a lot since. It seems to occur most often near to the back up time when the server goes down.