Rendering glitches with transparent shaders

[vi-technocat]

Godot Versions tested: 3.2.3, 3.3
Godot OpenVr versions tested: 1.1.0, 1.0.5
Headset: Valve Index
Graphics Card: GTX 1070
Nvidia Driver Version: 466.11

I'm not entirely sure if this is the right place to put this as it deals with rendering, but I'm working on a project that makes heavy use of screen-space shaders in VR, and I am facing this rendering glitch that I can't figure out why it's happening.

When using a transparent shader, either with a fragment shader on a colorRect attached to the ARVROrigin (like the Vignette effect in the VR starter tutorial, or a spatial shader attached to a plane that hovers in front of the camera, I get artifacts when looking through the headset at other geometry, like the geometry is shifting by half an inch depending on the normals repeatedly. It doesn't happen when looking at the Godot preview, only when looking through the headset.

It's hard to explain but can be seen in this clip by looking at the corners of the geometry:
https://user-images.githubusercontent.com/24375284/116797576-c0c27b80-aaac-11eb-8801-449839c99fb7.mp4

And here's a sample scene download:
https://nextcloud.hollandart.io/s/E6zoZR2wBqB4qqe

I know for version 4 Godot is getting a rendering update, and it seems most development has moved to the OpenXR plugin so maybe my issue will be fixed through those changes, but I'm on Windows for this project (the 1070 and VR on Linux doesn't work) and it's been a pain so I wanted to let y'all know about it and maybe get some insight into what is going wrong and if may be fixed with v4.