BigRail:
The combination you are using should work as that is what I have. ZW-C with 135 bricks, running TMCC then switched to Legacy.
You might ask the guys at 3rd rail under what conditions was the engine tested?
Do you have another layout near that you can test on?
If that fails, I suspect you may need to return the engine again... I know you said you would not want to do that, but you may not have any other choice if the above fails.
Good luck.
Charlie