Descent 2s appears to start golf app over my app

Hi,

I have an app where user presses start to begin a workout once inside the app. This has worked well for many years on all Garmin devices… Until today. 
Customer is complaining (and sent me a video of) the following behaviour:

  •  Press start to start workout
  •  Garmin leaves my app running in background, but launches what looks like a golf tracking app over the top (complete with message “Round 1 Press to mark round”)
  •  Garmin then notifies looking for GPS
  •  My app is unreachable but appears to be running in the background

 Can anyone explain what this might be? I’ve neither seen nor heard of anything similar and, as I say, my app has been live for years and has thousands of downloads. 
G