Is he supposed to just exit the conversation if you ask him about your next opponent after you beat Stygian Exorcist? If I hit "1" key or click on the first dialogue option, it immediately exits the conversation window.
EDIT: After talking to Lanista after winning against Stygian Exorcist and getting paid, I then exit the arena and garry gives his final speech. I talked to him earlier before getting my reward from the last fight.