I probably already said so in this thread, but my 925 has been having this issue whenever I listen to music. Just a couple of days back, I noticed it also occur in my 810, which is maddening! I thought it was only happening to my 925, but lo and behold, while listening to music and then pausing it for a moment, the sound then only played out of the left side when I pressed play again. Definitely an 8.1 specific issue because I never experienced this on either phone on 8, and my 920, which still runs on 8, has never had this problem.