The app use the phone clock as the source of time. If the clock is off the track replay will be ahead or behind comparing to other boats in the fleet. To avoid this problem the phone settings needs to be set to “enforce” correct clock time within a phone:
iOS: Settings -> General -> Date & Time -> Set Automatically ON.
Android: Settings -> Date & Time -> Automatic Date & Time ON.
The latest version of the app will prompt the user if the phone time does not match GPS time. Please make sure you and your fleet have the latest version of the app.