My textures are losing visibility in some areas. Why???

I brought in some vehicles from the city sample and retextured them (which is probably not the way to go, i know) but when i’ve added new textures, in some places, they lose visibility and look like the basic mesh. Any idea why this might be happening?

Thanks in advance!

No, but your term of Re-textured doesn’t really inspire any confidence for the end product.

Did you just change their textures - without knowing how they are used and why - or did you change the material entierly?

Also, I don’t think anyone can tell anything off that screenshot. Even if they made the assets…