Mask exports as thin shell

[GhostDog98]

If I export a mask (in this case the mega_sydney mask, units/pd2_dlc_swm/masks/msk_swm_sydney), it comes out like so:

Perfect! However, If we look at the back:

We can see it is infact a 1 shell thick object.

We can see the only closed geometry is infact within the "mask cushion" section.