Correct, the first screenshot was taken after the export, I had yet to apply her proportions and was in the process of doing so in a fresh scene. After opening the finished model in HLMV is when I had noticed the Face.DMX mesh marked as all sharps

I didn't run into any errors exporting, although I did have to cull the Weight link threshold.

Here's the Dropbox link to the files Yuzuki Files[www.dropbox.com] This should contain the .blend along with the DMX files

When exporting my model's Face mesh as a DMX results in all the faces marked as Sharps.
Face mesh DMX Export[cdn.discordapp.com] And the original Prior to DMX export[cdn.discordapp.com]
If I export as an SMD, the model works fine but does not preserve any shapekeys. Preferably I'd like to preserve the shapekeys and not have to export as a SMD then manually create the Face Flexes.

I've tried converting all Tris to Quads, this works. However the shapekeys are not preserved in the DMX, the only way to preserver them I've found is to keep the mesh Triangulated. However Triangulated faces result in the aforementioned issue.

I'm currently using Blender 2.93, Source Tools v3.1.1, I can provide .blend file along with DMX/SMD files