Continuity mistake: During the "We Don't Talk About Bruno" sequence. Towards the end when they are wrapping up the song and the family was circling around Mirabel. The animators accidentally added the "gold fish" woman instead of Dolores. When she leaves the scene for a split second they add her to the sequence. (00:49:16)
Other mistake: After Mirabel places candles in front of everyone's door, she stops to look at the wall of photos which each depict members of the family standing in front of their respective doors. In the photos, you see each member of the family as a child in front of their door, but the door they're standing by depicts them as adults. When Antonio gets his door, the door shows him as a child.
Continuity mistake: During Bruno's rap in All of You, when he is talking to Pepa the camera spins and you can see Abuela Alma standing to the left of Julietta, but a few seconds later when he goes to Julietta, Abuela Alma is nowhere to be seen. Julietta has also moved a few feet from in front of the arch door to the half collapsed wall.