Character mistake: In the finale of the third part of the collaboration with Street Fighter V, the announcer Serina's sign-off line is "That's all from SERNIA."
Revealing mistake: Rudy's "Judgment of Glory" Finisher uses a special background of distant mountains and cliffs. Sometimes (in particular during Mecha Goenitz's challenge) part of energy/fire or even whole enemies get in front of the superimposed image, casting shadows on it like a cheap theater background.
Other mistake: The railroad background seen at the beginning of KoF96 has a sign saying "Railroad CROSED."