I have the 1st gen Galaxy Active and the 1st gen Galaxy Buds.
I use them both for running and play Spotify from the watch which I've downloaded the tracks onto, however after about 15 minutes into my run, the buds start cutting out for like 0.5 seconds and music skips every so often. I don't get why this is happening.
Trying them at home, they're perfect. I can leave the watch the other end of the room and the music is flawless.
I am using a Spigen thin rubber case which protects the edges of the watch, but I doubt it's that as like I said, at home they're fine.