Metallic textures not copying across when building the Package

When building an aircraft Package, One of the liveries has a just couple of metallic textures that won’t build. The equivalent diffuse and normal map textures from the same material work fine but I can’t seem to be able to get those to work.

It only happens is one livery with three textures. Any ideas where I could have gone wrong?

Thanks in advance

Make sure you are using PNG textures. I use ORM-maker to make the composite files correctly. Try that program to make your composite for your textures.
[Though i have worked on metallic airport textures rather than aircraft. [ using Blender].