The smile of the face Usnavi draws on the cooler door constantly changes shape between shots.
During 'The Club', when Usnavi and Vanessa are finally together on the dance floor, Usnavi goes to get shots for the two of them, to Vanessa's dismay. She is shown disappointed as she looks in his direction. Then she is shown dancing again and having a good time. Then it goes back to her looking disappointed.
In the scene with the song "When The Sun Goes Down" there is a window air conditioner and some kind of cloth hanging on the railing behind Nina and Benny at the beginning of the scene but both are missing at the end.
The D Train doesn't run in the Heights, the A does. To get the D to the Bronx, you need to backtrack to 145th Street on the A, then transfer.
US Navy ships actually do not have "US NAVY' in large letters anywhere on the exteriors of their ships, only the hull number on either side of at the bow and the name of the ship across the stern. Usnavi's father would have had to see something else (perhaps a recruiting poster?) to get the inspiration for his son's name.
Evaporated milk and condensed milk are two different things. Yes, they are both canned but condensed milk is sweetened, evaporated milk is not.
The Bronx Grand Concourse address given for the new beauty shop is a residential block, there are no commercial businesses.
When Usnavi takes the garbage out and discovers the lease agreement in the trash the air conditioner compressor on the wall is clearly running (you can see the fan rotating) even though they are still in the blackout.
Abuela Claudia's "mother's secret recipe" for café con leche calls for "one can of condensed milk." When Usnavi prepares Kevin's coffee, he uses evaporated milk, which would spoil without refrigeration. She suggests condensed milk because it does not spoil if left out in the heat.
After "96,000", the children ask Usnavi who won the lottery. He answers that nobody knows, and that if he knew he would tell them. However, he found out who won later in the movie, and is telling the story years after it happened. So, he actually did know. Maybe he just said that he didn't know, but he actually did. In that case, it would have been more appropriate it to say that he would get to that later in the story.
In the Carnaval del Barrio number, Carla says she has a question, but she follows that up with a statement, not a question.
(At 1:53:36) When Nina and Benny are dancing along the outside of the building, the satellite dish is pointed north. As NYC is in the northern hemisphere, it should be pointed south.
Nina is shown to live a few blocks below the George Washington Bridge (which is at 178th Street). However, she gets on the 1 train to go to the airport above ground. The 1 train only goes above ground briefly at 125 St and then not again until Dyckman Street (about a mile above the bridge). There'd be no reason for her to get on the train either of those stops.
A musical number near the end of the film, on a fire escape and the wall of the building, the George Washington Bridge is seen to the North and the sun is setting beyond it. This is a mistake, since the sun has never set in the North.