Audio problem: Near the end, when the officers are getting out of the van, they are shouting "Hut! Hut! Hut!" but their lips aren't moving. (02:13:45)
Continuity mistake: After we've heard why it's so great to be an Illinois Nazi, there's a wide shot of Jake and Elwood's car in a queue, and a policeman walks past the driver's door. In the next shot, the cop hasn't yet walked past the door, and instead of doing so, he stops when the Blues Brothers ask what's going on. (00:56:14)
Continuity mistake: When Carrie Fisher first attacks the boys with rocket-propelled grenades at the hotel doorway, they dive for the sidewalk and are covered with debris. As they rise moments later and enter the hotel, their black suits and hats are covered in white cement dust. In the immediate next shot, as they climb the hotel staircase, their hats and suits have no dust whatsoever.
Revealing mistake: During the big chase scene at the end, right before the Nazis accidentally drive off the bridge, the Bluesmobile is seen doing a backflip over their car. Watch carefully as the Bluesmobile first lifts off the ground - an air-ram is visible firing under the car, which causes the car to begin the flip. (Note: This scene has been cropped in some releases so that the air-ram isn't visible, but it is still present in other releases of the film).
Continuity mistake: Near the end of the movie when the brothers are preforming "Sweet Home Chicago", they do a lot of spins and turns. The very last spin they do puts Jake towards the audience and Elwood towards the band. Then the camera angle is changed and Elwood is towards the audience and Jake is towards the band. (01:55:05)
Continuity mistake: When Carrie Fisher is shooting at Jake and Elwood in the tunnel under the Palace Hotel, she hits a water pipe and water sprays everywhere in a mist. In the next shot of Jake and Elwood lying in the mud, there's no spray visible behind them at all. When Jake stands up a few seconds later, the spray is back, but is more directed now. (01:57:39)