The game doesn’t like having it’s memory being externally edited as it could cause corruption.
As for Foxy and Freddy, they have been rebalanced so that foxy’s attacks are considerably lessened when you watch her run, and she can be locked more easily.
As for Freddy, she has been rebalanced so that she is an actual threat, as in the original she was incredibly absent.
Finally, the power consumption is a lot more lenient in this version compared to the original, netting you around an extra 10-14% extra.