Shape keys/blendshapes on models imported from Blender cause rendering glitches in HTML builds

[gdbongle]

Godot version

3.4.4.stable, 3.4.4.mono

System information

Windows 10, GLES3, AMD Radeon Vega 8, Driver 24.20.12028.4004

Issue description

When I add shape key data to a model in Blender and export it to Blender through the glTF format (both .gltf and .glb) it causes the model to have major graphical glitches specifically in HTML builds. Geometry data exported does not affect this issue. I also found someone else to test the project on a machine running Linux, and they didn't experience this issue when running the project with the Play button. As far as I can tell, the issue is only in HTML builds. Furthermore, it appears to occur on both Firefox and Google Chrome.

Here's the Windows build's results:

Here's the HTML build's results:

Steps to reproduce

Reproduction:

1. Create a model in Blender
2. Add a shape key to the model
3. Export the model to Blender with the glTF exporter
4. Place the model in a scene
5. Build the project for HTML
6. Run the built project

Minimal reproduction project:

1. Open project
2. Build for HTML, either through exporting or through the option in the top right
3. (Optional) Use the left and right arrow keys to progress the shape key

Minimal reproduction project

Bug Testing.zip

[Calinou]

Can you reproduce this after switching to GLES2 and exporting the project again?

[gdbongle]

@Calinou When I switch to GLES2, the bug does not occur in the same manner. The model instead completely disappears.

[nerdgamer2662]

Quick note, I accidentally used the wrong account to open this issue. If it is at all possible, I'd like future comments to tag this account specifically.