I have been using my Oneplus 3T on stable version 4.1.3 and every day I experience an episode when the phone doesn't play or record video (on any app including stock and 3rd party) and doesn't play notification sounds. This is temporarily fixed by a reboot but the problem resurfaces within 24 hours. I have tried clean flashing the OS from recovery and and adb sideload, both with no avail. For that reason I'm worried it could be a hardware problem, although I'm no expert.