The parameters are keywords. I forget the exact arguments but you will want to do something like bpy.ops.import_scene.smd(mode="NEWARMATURE"). Check the definition of the importer class to get the full list of what's available, or run the importer through the UI then check Blender's command history and see what it executed.

What happens if you compile the decompiled model without changing it?

Are you importing the QC from its original location, or have you moved it?

You've already posted this. I'm still waiting for your blend file.

It was still a bug that an error occurred. I just released 2.9.1 to fix the problem.

This isn't the place to ask about errors with your model. Try the Facepunch forums.

If the scene is configured for SMD export, there is a new Target Engine setting in the Source Engine Export panel.

Or, if the UI is drawing, you can select an item in the Source Engine Exportables list.

I've seen one other person have this problem. It's an issue when drawing the UI. You can fix it by heading to the scene tab, expanding the Custom Properties panel, and deleting the "vs" item. You'll need to re-enter your scene settings.

I managed to connect and upload the fix to the website.