Character mistake: At Duke Boudreau's bar, the potential recruits for the sting are told, "Gondorff is setting up a con on the North side". Later in the film, Agent Polk tells Lt. Snyder, "Gondorff is running a con on the South side". The actual address for the betting hall is not given, but it is just down the alley from Klein's, which does have a South side address.
Suggested correction: It's possible recruits were given the wrong information on purpose until they'd been cleared for participation. Misinformation is a good way to confuse and delay any unwanted attention.
This does not correct the posting. "Polk" tells Snyder that Gondorff is running a con on the NORTH side, which is incorrect. He has absolutely no reason to try to mislead Snyder.