The shadow Lucicolo was already caught in a previous battle with him and he now has a Shadow Politoed + several regular Ludicolo. I attempted the battle about three separate times taking different actions but each time once I had him down to one Pokemon and was about to finish off the battle, the game would freeze when I would select my moves. I don't think it's tied to one particular pokemon of his, because at least one time his final pokemon was the Politoed, while the other two times it was one of the Ludicolos but I can't remember which level(s) they were.
My team is Umbreon, Swampert, Sceptile, Clefable, Shelgon (all purified), and Shadow Alolan Marowak. I had a different combination of pokemon left on my own team for each crash, and also experimented with selecting different moves to see if there was one particular move that was causing it, but no matter what moves were picked, even if I chose an item or "Call", the game would freeze as soon as my choices were selected.
It may be related to a bug a user posted about a few posts back relating to status conditions, because I think in at least 2/3 of the scenarios or possibly all three his last pokemon had a status condition. I can try to attempt the battle again but make sure that his final Pokemon does not have a status condition.
EDIT: I just tried again and made sure not to inflict a status condition on his last Pokemon and was able to complete the battle without a crash! So I think that may have been the cause. I just want to thank you again for not only making this hack but being so dedicated to updating it and trying to fix these bugs.