So this bug has been around for a while now. It always screws with your head if you’re not aware of it. It is especially dangerous for people new to playcanvas, who don’t know this is a thing.
If you, in any playcanvas scene, first import a model that has materials. Then, you assign a different material to the model in the 3d program and export it again. When you reimport the model in playcanvas, the material change does not happen. In fact, you have to reimport the model twice for changes to occur.
Try it out for yourselves:
Link to models
In the zip-file, you’ll find two versions of the same model. The first version uses materials called “Red”, “Green”, and “Blue”. The second version uses a single material called “Yellow”. Follow the steps above, and see that when reimporting the second version, the “Yellow” material isn’t imported on the first try.