Maggie goes to dinner with her parents and Maxwell. The restaurant's large windows reveal it is still daylight. Sunset in December is before 4:30pm.
There were no women of color in the Rockettes at this time, dancers or staffers.
Many of the establishing shots of the New York skyline are clearly from the present day (2022) with modern buildings seen on the skyline that were not there in the 1950's.
Establishing shots of Radio City Music Hall are clearly from the present day and not the 1950's as many modern buildings, clearly built after the 1950's, are seen in the background.
Very inappropriate for the time. Almost all of the dancers would smoke cigarettes, and they would eat much less food, especially desserts.
When Maggie is given the information for auditions for The Rockettes, it reads Auditions for the The Radio City Rockettes. (the is repeated)
When Maggie and John walk to Rockefeller Center to look at the Christmas Tree, when looking at the tree, you see the Rockefeller Center building in the background and can see the NBC News logo. The movie was set in 1958, the NBC logo seen, was not correct for the movie's time period.
The Marathon model of Checker Cab existed in the mid-1950s, but examples with impact-absorbing bumpers were manufactured much later.