Black screen when unlocking

[Nadezhda Georgieva1]

Using Windows 10 Insider Preview Build 14946 and Insider Preview Build 14951, my Lumia 535
with both builds when pressing the power button - the phone is unlocked but the screen is black, when dragging the finger up, snapping is heard and the phone is unlocked but the screen remains black.
I did Hard Reset with build 14946.

 

[abhishek singh21]

clearly an optimization issue where it takes a long time to bring up the content after unlocking the phone be it start screen or an app. As you are on insiders this issue is very common and could persist until the final build after which we will start getting the cumulative updates. Hard resets may or may not fix this so as of now keep looking forward to a new build or you could roll back to the public build using windows device recovery tool from Microsoft.