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. We consider the symmetry of the situation. We can instead consider events from the perspective of the ladder. The ladder occupies its own inertial frame of reference. The same laws of physics apply. This is by the principle of relativity.