I am a problem with my phone and Garmin connect mobil (GCM). The smart notification of GCM is activated, the battery economy standby is deactivated and GCM, bluetooth services, strava are put in "not optimized" in "optimization of the battery".
Strava beacon or live track of GMC does not work. I think when the phone is in standby it cuts mobile data.
According to the forums it would be a problem of Android 8.0. Will there be an update to android 8.1 and 9.