Try to import the decal again to the original. And I'm not sure if 0 mips is normal but you did substitute the mipmap?
If you can't get it you could working upload the files and I'm sure someone can give it a go.
Yes, I do not think I 'm smart enough to figure this out so it would probably be better if someone who knows how to do, get paint and decal files and solves it in a simpler way .