I've found a solution for this. It seemed to only happen to me and my friends that have PartyLimitBegone installed. What we ended up doing was saving before entering the inn and having only 4 party members then:
1. Go to Steam > Library > Baldurs Gate III > Settings > Properties > Installed Files > Then click Verify Integrity of Game Files
2. Delete the Mods Folder in the Data folder
3. Play The game (Without the mod) (entering the last light inn for all of our campaigns had the strange ox as the ox and not a rampaging ooze)
4. Save and quit
5. Reinstall any mod we have (we only had PartyLimitBegone)
6. Play the game
After that everything seems to work fine.
Please keep a save or backup of your files handy just incase this doesn't work for you guys.
Happy Adventuring
