Other mistake: The credits for the Tarleton brothers in the opening credits have the twins switched with their actors. George Reeves doesn't play Brent, he plays Stuart. You know this because in the opening scene the two boys are talking about the party and asking Scarlett for dances, and George Reeves points at his brother and calls him "Brent."
Other mistake: When entering the Haunted Forest, the Scarecrow is carrying a pistol and a stick, the Lion has a bug sprayer and net, the Tin Man has a monkey wrench and his axe. But different scenes after that shows some items missing and then returning. I guess in the "Jitterbug" scene that was cut, they lost all those things but the axe. (01:13:15 - 01:16:00)