Metal textures from CoreVideo render black when SteamVR is enabled on Mac

I am attempting to render Metal textures obtained from the camera on macOS. To do this, I am using a core video capture session, and the resulting metal texture in a similar fashion to how the 4.18 ARKit plugin code works (i.e. avoiding CPU <-> GPU round trips).

This works as expected when VR mode is not enabled (i.e. SteamVR not running, and no headset connected when starting the editor).

However, when SteamVR is running (and an HMD connected) and the editor is started with ‘VR mode’ enabled, the rendered texture appears black, and occasionally flashes solid red/green/or blue.

Presumably this is either a macOS metal issue, a graphics driver issue, or a UE4 rendering issue. I am running macOS 10.12.6 and UE 4.18 on a MBP with nvidia 750M GPU (with Apple nvidia driver).

Any ideas as to the cause? Thanks in advance.

In addition, switching between forward and deferred render path doesn’t make a difference.

Going to answer my own question - updating to macOS High Sierra fixed the issue.