Using 5.4b21 I see weird shading issues on a terrain with grass details. The grass has billboarding disabled and works as expected in two pass rendering. When enabling single pass VR in Player settings, the shadow starts to separate from the geometry while turning. The first image shows the scene with the HMD locked in place. The second one shows a still taken while turning the HMD. You can see how the grass shadows are offset from the grass geometry.