At the end of the game, the bots will show which hand they were working toward so you can see what they were aiming for. Level 2 and Level 3 bots also have the ability to play defensively.
This means that if they determine they are unlikely to win, they may break the hand they were working toward and begin throwing tiles they believe other players don’t need - potentially even jokers - rather than risk discarding a hot tile that could allow you (or another bot) to Mahj. When this happens, the bot will indicate "(I broke my hand)" so you know that’s what occurred.
Please note that when a bot breaks its hand, the tiles you see at the end of the game may make it look as though the bot was playing poorly. In reality, it may have had a strong hand that it intentionally abandoned, and the tiles shown are simply the result of its defensive play.