This seems to be a classic case of experimenters not properly understanding their own experiment. A faster-than-light propagation would nullify everything currently known about physics and every experiment ever performed. So the most probable explanation is experimental error. Moving on to the phenomenon itself, it seems all they’ve done is create a relatively narrow beam of high-energy radiation which, thanks to the fact that massless photons nevertheless carry force, would result in deformation of any material placed in front of the beam. Regarding measurement of resulting energy versus input energy, every time someone’s claimed greater output than input it’s been shown that they simply didn’t understand the actual inputs generated by their experimental setup.

All in all, I wouldn’t hold my breath on this one…

Anyone who enjoys my articles here on Medium may be interested in my books Why Democracy Failed and The Praying Ape, both available from Amazon.