User blog comment:Omega natsu2/Fairy Tail Episode 204: Stake My Life on Hospitality, Review./@comment-24622358-20141020044525/@comment-7418318-20141020074630

They did come into direct contact with the Gate twice, once when unlocking it and then again when closing it. And later a few of them (or all of them in the manga) also attacked it. At one of those contacts, or maybe due to the repeated contact, something probably happened to them.