At around the 25 min mark. When Claire, Andy and Mark are on their bicycles in front on the nine crosses, at one point the camera shows Mark on his bicycle. In the very next shot he is standing beside it and in the third, he is again sitting on it.
A fake newspaper headline is dated Sunday, April 28, 1961 on a weekly paper that, according to the masthead, is published each Friday. April 28, 1961 was indeed a Friday, but the actual date published on the masthead says "Sunday."
At the ice cream shop, Claire orders a two-scoop cone but is given a cone with only one scoop.
Andy claims he could win the 200m freestyle by not breathing at all, but he loses by a stroke. Even Olympic-level athletes breathe at least every four strokes. If Andy was in good enough shape to race 200 meters fast without breathing, he should be able to break records with proper breathing.