The model looks fine in blender (texture, material, and render), but when I run my app the parts of the model don't show.
The normals have been recalculated and flipped many times (sometimes only affected areas too) and all doubles are removed yet nothing seems to change.
By playing around with settings I've been able to get better and worse results, here's the best result I've gotten:
(doesn't seem to be changed by culling settings) and here are all my settings:
All textures and materials have the same setting applied, the missing bits have the same textures and materials as the non-missing bits