I have noticed, and there was some other forums people was looking for a fix..
I found simple and and weird fix
If you turn on (Settings>Device>Sound>Screen lock sounds) lock sounds, and you cant hear any sound when unlocking, theres a simple but weird bug to enable it:
1. Go to: Settings>Device>Wallpaper>Home and lock screens
2. Choose Live wallpapers
3. Choose one of live wallpapers. (I got only two one that came with software Bubbles and Phase Beam, but im sure that would work with others also, Test by yourself.)
4. So now you can lock/unlock with sound. Yes i know the sound is way different than was before
Hope you enjoy my finding.