Because I use the S-View cover what I do is close it and open it again and what is actually does is wake the screen. Seems like a "wake screen" bug to me, and I don't think that the proximity sensor in the settings menu can help with that, it probably works only with stock dialer and not always with third party apps like Viber. So I don't know if you try to press the power once in order to close the black screen and then open it again if it helps.
Galaxy Note III N9005 (4.4.2)
iPhone 4S (iOS 7 JB)
HTC HD2 (pdaimatejam Rom Wp7.8 OS 7.10.8862.144)