Map Boss Arena Bug

Clearing a map and got to the boss arena where I simply walked into the area and fought the boss. Killed it and went to backtrack to my breach that I was saving for the end. There is now a red wall blocking the exit from the arena with a "Arena" portal (like moving to a next map in the campaign) that is on the other side of the red wall. Can't click on that portal or move passed the red wall, thus losing my breach.

Keep having this happening randomly. Not every boss blocks off with an arena portal, but every one that does is behind the red "door" blocking the exit.

I have tried this aswell on the map "Steaming Springs" after killing "Manassa, The Serpent Queen"