Was switching to DX11/Vulcan the only way you resolved the issue? We have the same issue, and would like to keep DX12 support.
One thing I have noticed is that changing the ScreenPercentage value the amount of visual distortion would change making it feel like a screen space effect that’s gone awry.
Update:
More digging and research, this happens when the screen percentage is above 80, below 80 the issue doesn’t visually present like this. You can however see that the ambient occlusion pass is only being applied to the left eye and slightly flickery so I think it’s related to SSAO getting enabled in VR.
