Materials and Textures on Windows and Doors appearing all white

Basically, I am helping to work on an application that allows users to create models of buildings and houses, then export those models into a mobile app that displays those models in the real world via AR. However, whenever doors or windows are attached to walls, they appear fine in the models before exporting, but when you see them via AR, they appear all white. I’m honestly pretty lost as to how to fix this issue, so I was hoping someone here would know.

Before exporting: https://i.stack.imgur.com/MFI7y.png

After exporting: https://i.stack.imgur.com/aAmPM.png

I’m also thinking this may be more of a export script and/or shader issue. What do you guys think?