JP1 Velociraptor transfer incident Q.

-In the fist movie introduction, when the transferal of the Velociraptor via prison crate to the pen, the gate keeper is mauled when the Velociraptor races through, dislocating the link between the crate and the pen. -How could this possibly happen? Isn't the crate secured to the entry gate by protracted steel lugs and/ or rods internally at the entrance point, exactly like a bank vault? Obviously the lights are an electronic confirmation system; the gateway can only be moved manually at lock confirmation, as a practical security measure. If the Velociraptor prison crate is anchored in place by multiple, industrial strength steel rods, how could the slippage accident possibly happen? Does any one know the "explained" story of what happened?