PostProcessing-Stack V2 (Layer) affects other shaders (e.g. Custom Water-Shader (Waterreflection))

Hi there,

i am working/ fooling around with VR in Unity 2017.4 .
I also started to look into the Post-Processing-Stack V2, to make use of HDR-Emission.
In my project there is a custom water-shader with reflection etc. too.

THE PROBLEM
The custom water reflection (Shader) is wrong on both cam-eyes in there own way (Offset), when i put/ turn on the "Post-Processing-Layer" on a camera/ the cameras. Turning the "Layers" off fixes everything but i can not use the PostProcessing-Layer without causing an offset of the water-reflection on each eye again.

I do not have enough knowledge (allmost none) when in comes down to shaders.
Does it have to do with something like "Render-Order" etc.?

I can not show u the water shader code itself...
Sry!