I agree with Shena - this does appear to be this year's 'temperamental' mission model!
It requires precise positioning of the 2 base red beams with the dual lock, as well as ensuring that pieces on both sides of the model have been connected fully, but not so tightly that the hinge axle doesn't let the hammer fall freely.
Note that points for this mission are awarded for ACTIVATING the wheel-roller and if the model at your tournament fails to release the wheel because the model is faulty or was set up incorrectly, you'd still get the points.
Chris