Skinned Rig does not import properly

I have a skinned rig, nothing special. It was made in blender and rigged in blender.
The problem is when I try to import it into Roblox via FBX, I get this error.

This Error ONLY shows up when the model is rigged. If I choose not to import the armature then the model loads fine and I don’t know what I’m doing wrong.

Import settings.

The model is just about 21k Triangles if that means anything.

P.S. The warning is just for the model not being water tight. Even when fixed the issue persists. And the same warning is present when its not rigged.

Edit: Well looks like it only works with the avatar importer, which is being deprecated now. So I guess this should be a bug report. But if anyone knows of any other issue that I might be doing wrong before having to report it. That would be appreciated.