Help Needed "Blank Screen Instead Lock Screen" Some Times

Hello Developers
I Have Lenovo K3 Note
Indian Variant K50A40
Updated To Latest
K50a40_s121_150813_row
I Faces Many Problems With Stock ROM (Like Touch Screen , Lagging And Network Problems ETC)
So I Decided To Flash A Custom ROM
Downloaded
Aosp ROM
Successfully Flashed With CWM Recovery
Without Any Errors
But After Few Minutes Of Using
Phone Goes To Blank Screen After Lock
(I mean Blank Screen Instead of Lock Screen)
Now Tried Many Times Lock Button
But Same Blank Screen
I Have Removed Battery And Put Again
Phone Again Working Fine
But After Few Minutes
Again Same Problem
So I Thought This Is A ROM Bug
So I Have Downloaded Other ROM

Nexus ROM
And Flashed successfully
After Using Of An Hour

Same Problem Starts In Nexus ROM

Then Downloaded The Official Dev ROM VibeUI_2.8_1540
And Flashed That
But Same Problem Again On This ROM Also

So I Have Flashed Stock ROM With SP Flashtools
In Stock ROM , There Is No Problems Like That

So I Have Flashed Again custom ROM
But Again Same Problem,, revert back to stock
Facebook Developers Says I Am First Who Facing This Type Of Issue
So Please Anyone Help