Continuity mistake: Reverse Flash knocks Flash back and he is next to the edge of a building, his arm hanging over the side. Flash sees Grifter get killed and tries to get up, but Reverse Flash presses him back down with his foot. Flash is still right next to the edge of the destroyed building. The Reverse Flash zooms around behind Flash, and suddenly there is at least a good 2 feet between Flash and the edge. Moments later, Reverse Flash kicks Flash and he goes over to the edge again.
Picture added by Quantom X