Pause-modus on garmin vivoactive 3 music

I got some problems with my hike 2+ app which I use with my garmin vivoactive 3 music. During the first 1 or 2 hours of hiking everything is tracked and fine. But then the app always pauses while I'm still walking on and don't even touch the screen and stops tracking the hike. Today I did a 17.6km hike with 1360hm which was safed as 6.9km and the way straight down instead of all the curves we did. Can I change that somewhere in the settings or what is the problem of this not-tracking function which happened the third time today (more or less always on the way down)