In Avengers: Endgame, the mistakes primarily seem to be centered around simple continuity issues. Users noted that when Thor talks to Valkyrie at the end of the film, his beard has been trimmed short; then, in the next scene, when he’s arguing with Quill, his beard is longer. The crepe in the breakfast scene goes from being whole, to cut in two, and then back to being whole again. And during the final battle, Ant-Man can be seen in two places at once — in the van, and in his giant form, fighting alongside the other Avengers.
Article source: https://www.cinemablend.com/news/2486304/captain-marvel-and-avengers-endgame-top-2019s-movie-mistakes-list