Continuity mistake: In the third segment of the movie we see Davis, Yolei, Cody and their Digimon playing on the beach. In the wide shot when we see all of them playing we see that Davi's Digimon is in his "rookie" form, Veemon. When they show a closeup of him and Davis together, Veemon is now in his "in training" form DemiVeemon. Then they show them all playing again and he is now Veemon again.
Other mistake: When Tai is typing an e-mail of apology to Sora, he accidentally types "Love Tai" as opposed to "From Tai" which he finds more appropriate. At that moment, Kari walks in, resulting in Tai's embarrassed stumble into the keyboard. We then see a highlighted "From Tai" change into "Love Tai". It is possible that Tai had already changed it before we saw it and then accidentally pushed Ctrl+Z upon Kari's arrival, but this is more than doubtful.