Try installing an older Garmin Connect Mobile app from a public APK archive. With that method you'll see whether it is caused by a recent update in GCM. If so, then you can report it to Garmin, and ask whether they could change it. If you find that the older version makes no difference, then it comes from your watch - perhaps you have changed some settings in the activity in the meantime. You could try the factory reset (master reset), if you do not mind having to reconfigure the watch again.