Near the end of the story, Prof. Arturo and Rembrandt exit a cave and take cover behind a chest-high boulder. One of them accidentally bumps the boulder, which then easily rocks back and forth a few times.
Obvious stunt double when Quinn falls off the dune buggy and fights Cutter.
When Remy and group were hiding behind boulders while the bikers were riding by, Rembrandt picks up a rock and throws it towards the camera. The rock curves and rises up as if made of Styrofoam.
When Quinn activates the timer to form the vortex at the end, the angle of the beam doesn't align with how he pointed the timer.