When “Exchange” was used in a 2v2 tag duel, turn player could only select one out of the 4 cards in the opponent’s hand, and the opponent could not select the only card in the turn player’s hand, which locked up the duel because “Exchange” couldn’t resolve and forced us to surrender.
To replicate, I don’t know how picky this is. There’s a chance it’s as simple as playing “Exchange” in any situation in a tag duel. Or, it may depend on something relating to which team slots each player is in. The severity of the issue may depend on how many cards are in each player’s hand, because it seemed like the only reason our duel locked up was because one player only had 1 card in their hand.
Replay code: https://pastebin.com/tBwwyi83
Obviously “Exchange” should’ve just resolved properly, letting both players pick a card out of their opponent’s hand and then letting the turn/game progress.