OVR_InitRenderThread() entry GL Error: GL_INVALID_OPERATION

Hello,

I just brute forced my way through a terrible problem and I want to post it here so that future selves don't have to go through the same pain.

I have a Unity project using the integrated VR that I'm running on a Note4 GearVR. The Unity version doesn't seem to matter but I was mostly on 5.3.4p1 with the OVR 1.3.0 plugin patch and the OVR utilities package.

It seems if I have a ShaderVariantGroup in the Shader Preload setting on the project Graphics Settings page i get this in my logcat:
OVR_InitRenderThread() entry GL Error: GL_INVALID_OPERATION
Which seems to mean OVR didn't make the FBO it needs and so nothing renders. Multitasking in and out of the app fixes it.
Nothing bad happens if I don't have VR support enabled.

I was bashing on this trying to figure out what was going on. I had one project that worked and one that didn't. And after smashing this project to pieces I found the issue was the ShaderVariantCollection. The collection itself has a bunch of standard shader variants, some particle ones, some legacy ones. Nothing custom. 

OpenGL ES Trace wasn't liking it either, so I didn't dig deeper into the gl error.
So that's a thing, don't know what or why.

But if you get this invalid operation on start up then maybe this will help you.

Cheers,
Joe