Black artifacting on Unity 5.3 with Android

I've been playing with my GearVR and one of my projects has developed some kind of black artifacting. I've diffed it against a project that doesn't have it and I can't quite seem to understand what is happening here. I've tried a lot of things and it persists. The artifacting happens on all shapes (basic primitives) and they have a basic material that's simply color being passed in. There is one directional light active, and it's the default one that starts in each scene. Anything in hard shadow doesn't have the artifacting. It happens with VR off, as well.

This is with Unity 5.3.0f4 building to my Samsung Galaxy S6 running Android 5.1.1. I built it on a 64-bit Windows 10 machine and my installed Android SDK is 5.0.

It's fine in editor, but breaks when played on my S6. It appears to affect framerate as well; it feels rather sluggish.

See attached image. Thoughts? Any information I can provide?