Haven't tested this on other battle modes yet...
I go into Mod Battles and select a stage. I then go to borrow hero screen and select someone to join my team. Then from the team formation screen I click and hold on the borrowed hero to view it. I go back to the team select and click to start the battle. It immediate goes into an error and asks to restart. Happens every time. Easy work around to only view the borrowed hero from the borrowed hero selection screen and not your team formation screen. But still a bug fix to add to the list
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