Why does my media volume ramp down automatically?

[AC Question]

On my s7 edge, when I play any media, the volume ramps down automatically, after 2 or 3 or 7sec. Just depends on the mood.

Now, the media volume slider does not change, just the actual sound. The audio may come back at times, but only for a second or two.

I've checked settings, uninstalled recently installed apps, checked the headphone jack. I'm at a loss.