Shader sometimes renders black vertices which involves compute shader, unlit shader

Hi, I have a compute shader code which decides the position of vertices. And unlit shader code which gives color to these vertices. It works fine most of the times. But sometimes rarely all vertices appear in black.
I am also using instances of compute shader, as I need multiple of them to run parallelly.

It happens only in single pass stereo, with VR set up (using HTC Vive). Using Unity version -2017.2.0f3.

Anyone has any idea why it's happening so?

 

Hi, does anyone know why so?