This might also help in figuring out what's going on. This is after dropping the airplane_auv shader on. There's a global "Default 1" shader, but then there's the unmapped starting Wings 3D material also called "default" and then there's the other material with the UV map "airplane_auv". What seems to be going on is that it's ignoring (or forgeting) the shading domains and applying the (unwanted) global shader to some parts of the model.

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Barbequed Pixels?

Your friendly neighborhood Wings3D nut.
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There might be something worth downloading.