Relevant TODO can be found in banker.py get_client_by_socket() function. Search for "TODO" using ctrl-f and you'll find it in a large commented block. Please read the whole comment.

The idea here is, when the banker is searching through its locally saved list of players, it will return the first player with the same IP address which it's searching for. An issue will arise, then, for example, whenever you expect the second player to be returned in this context, but you are running everything locally [on the same IP]. Thus, you will return the first player, not the second, which will lead to undesirable behavior. I also think this is what is causing tic tac toe to fail locally, so it's pretty important that this becomes more robust.

DM on Discord if you need help or more clarification (username: indev31).