I think something minor did happen, but it’s been exaggerated by the choice of words of the people on Twitter. Even the slightest shunt of two trains would cause a loud noise and a bit of hysteria from the ride hosts, and “the queue line being completely evacuated” probably just means that the ride was closed so people were asked to leave the queue. If it was more serious we’d know by now. It was probably just an unexpected rollback and the ride is probably closed to investigate the cause and to do some cosmetic repairs on the two trains.