When Sulu is seen as captain on the U.S.S. Excelsior, the master systems display (MSD) at the rear of the bridge is for the modified Excelsior class starship (like the Enterprise-B) and not the original, which the Excelsior is.
When McCoy, Spock and Kirk are discussing Alana's condition near the climax, Kirk's hair parts the other way in a couple of close-ups. These shots were flipped to make him face the right direction.