I have had mine exactly a week and I started to have the same problem yesterday. It occurred after they pushed Google Play and a few other updates down. Phone is not rooted. I have gotten the sound to come back on a few times but it eventually quits working.
I removed a widget that enables/disables bluetooth because it seemed like enable/disable of bt seemed to resolve the sound problem. I don't think that was the problem. I also removed a smart actions for testing purposes but I am not convinced they were the cause.
Shutdown and restart in safe mode did not seem to make a difference. A hard reset made the sound work again the first time I ran into the problem. The sound is currently working again right now. If I continue to have the problem it will be off to Verizon for a new phone.