What about the part that the wave is reflected back to the otherside of the cavity? Does it not just - reflect back and forth technically creating a net thrust of zero? I thought that guy claimed the slots inside the drive were the key to it's operation, yet the null device - one which did not contain the slots - worked the same.
Here's my past experience with microwave experiments: the damn things interferes with all your instruments in the most absurd of ways.
Don't believe me? Go take any normal voltmeter, remove the probe leads, and run the microwave with the door open (by passing the interlock of course) for just 5 seconds within a few feet of it - you'll get voltage reading. If you're not getting a reading then you are probably using a well shielded device - likely a Fluke or Keithley meter. Even those meters will likely show something still, I'd be impressed if they didn't.
So them measuring something like a few milliNewtons on a device that probably measures small signals and using even 50W in an enclosed cavity nearby - which itself will reemit some radio waves - on a metal table or in a steel vacuum chamber, where their own simulations show a large magnetic field gradient from one end of the device to the other - is enough evidence for me at least to show they're fooling themselves.