My S4 keeps turning down ringtone and call volume on its own. I really hate the rocker switch. I have to be very careful when holding the phone NOT to hit it and turn down volume, but it still is a problem.
I don't think I am now hitting the damn rocker switch, but STILL I am missing calls, and when I look at settings>device>sound the ringtone is at zero and there is a slash through the speaker icon and zero ringtone and often, but not always, the incall volume also. I turn them both up to max, but, at irregular intervals, it turns them down again.