Mine has been faultless until its first long ride yesterday - 56 miles and at 46 miles it began dropping the gps signal for minutes at a time, briefly reconnecting and then dropping again over 10 miles or so, when it went back to normal. It gave me straight lines on my Strava route map and several speed spike of 486mph, which messed up my averages rather. This was in open countryside, no rain, and with a GPS accuracy reading, in between disconnects, of 5-10. Others on the Wahoo google forum have seen this behaviour on longer rides. My bolt has also developed a slight rattle in the supplied mount.
I've never had an issue with the app, used it to set the Bolt up and again for a couple of tweeks, it doesn't run in the background for me (Android). My uploads are automatic via wifi as soon as I get home - works perfectly.