V5 Grey lines made worse in VR

[B738]

In certain weather where it’s misty or cloud low down I’m getting strange horizontal lines be not a blended merge or colour change. This is made worse in VR.  See 2d attached. 
 

Any ideas how to fix them?  I’ve turned most settings off to help VR including cloud blending as per the manual.

[B738]

Fixed it by changing the cloud merge but has impact on performance in VR