Okay sweet so I've managed to narrow down the issue to the fact that if the Pokemon does not have a full moveset, the game will not allow you to choose any attacking moves. I have no clue why this causes the issue, but I have finally narrowed it down to this. I have done multiple tests with different pokemon and moves and it seems that if the Pokemon you are using does not have a full moveset, the plugin will not be able to do what it needs to in the battle_scene_menus script at section 200. Sadly I am not a coder and thus I do not know the solution, but that is the bug.