USB stops working when Vin is 12V

USB stops working when I apply 12V to Vin. But, it does work when I apply 5V to Vin.

Does this mean I have a bad board, or is this a design flaw?

It seems to me that my USB hub is detecting the presence of voltage on the USB 5V line and shutting down that com port. Maybe the leakage through the Shottky diode is enough to "fool" the system.
Has anyone else seen this? Is there a solution that doesn't involve removing a part from the Nano board?