The building used in the prison scene is one that is wholly inadequate for its purpose. Chief Cooper refers to the inmates as "...serial killers, hit men and the worst scum on earth...", yet there are corridors with large windows with unreinforced glass; interior scenes show as many as six occupants per cell and mixed male and female populations in the same cell block. Furthermore, Pike is able to shoot out the lock on an access tunnel with one shot. None of these conditions would be considered adequate for a prison holding the kinds of criminals the chief described.
One third-act scene finds two Dark Riders left behind at the gang's lair as lookouts. They argue over stereo volume level before Flash speeds past and punches them out. Presumably meant to hit the floor out of frame, the one who demanded the music stay loud can be seen breaking his fall with his arms before switching to a limp sprawl.
As Jay Allen opens a wrapped present from his brother Barry Allen, the wrapping paper he is holding disappears and reappears as the scene progresses.
At the 8 minute mark when Barry is taking samples from the 'pavement' after the first attack you can see the fake asphalt flexing while he's scraping it.