Animal Companion taking up slot for party member

After meeting Nenio and reforming my party, my cavalier’s mount is preventing me from having a 6th party member. Before having to reform, my party consisted of Cavalier and Mount, Seelah, Lann, Ember, Camilla, and Woljif. This bug must’ve shown up after launch because I did not have this problem within the first couple of days.

I saw this bug once but I think the mount came back after the rest.