Could the theory which predicted gravitational waves be wrong?

The detection of gravitational waves scooped the 2017 Nobel physics prize. But in a Perimeter Institute lecture Erik Verlinde proposes a rather different theory of gravity

One of those big open questions that we have in physics goes like this.

Einstein's theory of General Relativity is elegant and accurate. It makes many correct predictions, including the prediction of gravitational waves, the observation of which won the Nobel Prize in physics today. Yet if we use General Relativity to predict the motion of galaxies, we get the wrong answer.