Tried joining a party for Urgent Quests and up comes a message that I wasn't able to join the party because the party was in a "special arena"? I'm uncertain if this is supposed to be a feature or if it's truly a bug because I went down the entire line of parties and tried every one of them and got the same message.

This hasn't been an issue with only Urgent Quests I've had this issue a few times with other expeditions and quests but this is the first one where every party is inaccessible. I've attached a screenshot to give you an example of what I mean.

This happens when the party has already initiated the teleporter to the boss/etc. It's not a bug since it's been in the JP version for a long, long time. it also happens on the yet-to-be-released "Level-Up Quests"

Most of those parties are only seconds old though; unless the entirety of that map is a special arena (which probably isn't the smartest idea since no one can join in progress missions).