The big problem with all of the positive results from the EMDrive experiments is that -- without a single exception AFAIK -- the observed thrust doesn't stop immediately when they kill the power. It decays exactly as you'd expect if you were watching something cool off. Obviously that's a very strong and obvious indication of experimental error.
I did some back of the envelope calculations of the latest experiment that seems to imply that most of the 'tapering off' could simply be inertia since the direct neasurement was deflection distance, and the apparatus is very heavy compared to the force measured. A part of it definitely looks like a heating related effect because of the nonlinearity, but at the same time the implied cooling rate seems to fast for moderately hot equipment in a vacuum.
At this stage I don't think you can claim the measurements are obviously wrong without actually calculating heat loss rates and how heat expansion would affect measurement with the given equipment asymmetries.
The radiation would die away pretty quickly. It would be determined by the cavity Q, basically. Think about a bell that takes a long time to fall silent after it's rung. With radio waves near c instead of physical acoustic vibrations, you'd need an insanely high cavity Q, well into the millions, to keep the energy from dying out in milliseconds. But cavities used in this type of experiment probably don't exceed Q=1000.
This kind of "ringdown" effect can be observed at human-compatible timescales at low HF frequencies in crystal resonators. But only a fast oscilloscope will let you observe it in a cavity.
You'd expect the signal to dissipate even more quickly in a case like that, where it's being made to do work by pushing against an ether or otherwise interacting with something besides the cavity itself.
But it's premature to speculate on what might be happening at that level of detail.
I may be thinking about this wrong, but think of a boat being propelled by a motor. When you turn off the motor the boat doesn't just stop. Inertia continues carrying it forward as the friction of water absorbs its momentum until it comes to a rest.
You could get similar charts between the EM drive cooling off as a boat slows down.
I agree that it's vanishingly unlikely that the EMDrive is doing anything but wasting electricity. But it's more productive to call attention to specific problems with the published research, rather than to wave your hands and issue a generalized bullshit call.
