Other mistake: During the Baer and Braddock fight, when the camera angle is from far away, you can see that Braddock is not actually connecting with his punches on Baer. Yet Baer still reacts like he's been hit. This also true with Baer hitting Braddock when the camera is showing the fight from far away in the stands.
Other mistake: During the opening scene of the movie with one of Braddock's boxing matches, he wins midway through the 2nd round. Yet, the clock on the wall behind the ring is straight-up, indicating that the clock had not even been started.