When you are seeing a report about an amazing breakthrough in science without any reference to scientific sources you better remain a little bit skeptical (or you might getting disappointed later ;).

Same goes here. Please read https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster
Looks like marginal thrust measured in those experiments were errors in experimental setup.

I'm personally putting my money on Mr. Newton and his Third Law ;)

"Law III: To every action there is always opposed an equal reaction: or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts."