Thank you for your query. The relevant department may serve you better/speedily, if you can provide logs/video by registering this feedback in Error Section (Samsung Members App -> Feedback -> Questions/Errors -> Create -> Error reports).
I connected earphone on my c9 pro and started music but guess what there was no sound coming in my earphones, i played many different songs, still no sound, and then i went to video player to play any video, the video started but freezed while its audio was playing and i was able to hear the sound in my earphone for videos, while the video was freezed and lagging. But then i closed video player to play music but still no sound, then i closed everything, and locked the phone and guess what i listened the phone lock sound in my earphones. I removed the earphone and connected once more and played the song from always on display, it played, still video lagging, and same music player problems while connecting the earphones when the phone is not locked. I did reset app preference, the problems were still there in safe mode also, i factory reset my phone still having problems. I use earphone 6 to 7 hours daily, but now i cant even the youtube video is lagging while earphones connected.