The apparent paradox comes when we consider the symmetry of the situation: we can instead consider events from the perspective of the ladder, which occupies its own inertial frame of reference, where, by the principle of relativity, the same laws of physics apply.
The apparent paradox comes when we consider the symmetry of the situation. As the ladder is moving at constant velocity in the inertial frame of the garage, an observer moving with the ladder also occupies an inertial frame, where, by the principle of relativity, the same laws of physics apply.