Other mistake: Right at the beginning of the movie, when Lewis's real mum picks him up from the box and hugs him, it's no more than three seconds before she hears Lewis from the future slipping on the step. She gets scared and puts baby Lewis back in the box. When Wilbur takes Lewis to meet his mum, near the end of the movie, the time his mum holds the baby is more than twenty five seconds.
Other mistake: In the beginning, when Goob falls asleep, he misses the catch, by almost a foot or so. At the end of the movie when Lewis calls out to Goob, the ball lands on his head, and drops into his hand. Since Lewis didn't alter the timeline to where Goob is standing, (as to the part of not inventing the helping hat) Goop should have been in the same spot.