Revealing mistake: When Margaret falls from the boat, she is floating with her shoulders well above the water, probably due to a hidden flotation device. Her outfit was too tight to trap any air for buoyancy, and a fully clothed person would normally be up to their neck in the water.
Revealing mistake: During the scene in New York City when Margaret proposes, a Boston police car is quite noticeable in the background. (Filming took place in Massachusetts, not NYC.)
Revealing mistake: At the beginning of the movie, when Ryan has the two coffees, he walks by a store and you can see a young kid hanging out the window using his cell phone to film him walking.
