Not sure I can help, but can add a bit of perspective - I downloaded the American Airlines livery for this plane, which was fine - except the engines and pylons were grey rather than painted. The zip stated that it was the Rolls Royce engined version, but I only got the engines to show up correctly painted when I substituted a different engined model.

So perhaps try using one of the three different Meljet 777 models to see if it makes any difference?

Good luck!