This glitch isn't particularly new, in fact I've experienced it since Khrysalis Part 2 first came out, but I've only been able to comment about it now.
If a player defeats Morganthe with their music volume on, the Shadow Combat theme will still remain playing even after her defeat animation, and during her final cutscene. It's very distracting from the rest of it, and I can't recall any other dungeons with this problem. I've tried it on different computers to see if it was just an error on the client side, but the music will still play regardless.