Using GLES3 causes rendering issues with Blend Keys

[Ongnissim]

Hello!

I know that the documentation recommends using GLES2, and I have been for most of my development time, but there is an object that I wish to animate with Blend Keys, and I found out today that GLES2 doesn't support blend keys.

Everything else in my game is running fine in GLES3, but these objects, which run perfectly fine in Godot outside of the quest, show up as mangled meshes, with black noise over most of the shader materials.

I don't have any of the spatial material properties turned on that are unsupported by GLES2, and what's most frustrating is that I can see it trying to work.

I have all of the rest of the settings to their default values, as far as in the Rendering Quality section of Project Settings.

I'm hoping someone can help :). It's difficult for me to think of a way to animate these morphing geometric shapes without shape keys, and I'd rather not do without them.

Thanks for your time!

Edit: Here are some images of what's going on---

On Desktop:

On the Quest: