Medusa does not have role block immunity, so you should not have been able to kill the Consort on Night 5.
Did you receive the role-block notifications both times? If you did not receive the notification on Night 5, the Consort might have been duelled by a Pirate. There is a bug revolving around Pirate negating the abilities of role-block immune roles, but not preventing their visits.
You can find more information on the Pirate bug on this thread:
viewtopic.php?f=10&t=111476