There doesn’t have to be a code error for textures to not be displayed correctly. I recently wrote a texture array loader because two people in the forum asked for it and I also needed it myself. During extensive tests I also had the case that some textures were not loaded before the code continued to run. The reason was that the callback was executed before all textures was loaded. Such errors can be very troublesome because they are not an error in the code but rather an error in the code architecture.
I then used await async to make sure that textures were loaded with certainty.
Here you can see how I load 6 2k textures relative fast.
As far as I can tell, the gltf loader does that too. I have already loaded models that used several 4k textures and it took a long time to load. The textures were always there.
If you had an example code it might help narrow down the cause.