The reason why the collar corrects your dog when placed inside a metal crate is exactly the same as above. Briefly, what causes colors to lose the signal emitted by the transmitter causes the color to apply the correction. With that in mind, there are several reasons why amendments are made during calibration. A large metal object instantly occluded the transmitter and blocked all signal radiation. The straight path between the transmitter and the dog could have been temporarily blocked by something interfering with the signal car / track, for example. In addition, your dog has his neck still in the pet zone, but you can stand on the back beyond the boundary line. Your dog can rotate 90 degrees, suddenly the collar is located outside the safe area and delivers the correction.