Pixel Depth Offset being ignored

I’m using UE4’s material editor. I have a custom sky sphere with a custom depth texture that is writing to pixel depth offset. It’s working in editor & PC but not on device on Android. I’m targeting the GearVR. It’s like gl_FragDepth isn’t being written to at all on device.

The same issue occurs on UE 4.16 and 4.17. Targeting OpenGL ES 3.1.

I’ve made a pull request here to fix this issue: https://github.com/EpicGames/UnrealEngine/pull/3915