Continuity mistake: When John sees his photos on Sarah's website, the lower row of photos shows him throwing a football. However, when Sarah took those photos earlier, she only took out her camera AFTER he threw the football, while John was already talking to Sam.
Continuity mistake: When we first are introduced to John on the Waverider we are shown his pendant swinging freely in front of his life vest. However in the shots after we do not see the pendant (or the chain if it was put into his lifejacket) including the flip on the wake. However when he pulls back up to the beach and takes off the vest the pendant magically reappears.
Factual error: When they are in paradise the law enforcement is all wrong from the uniforms to the cars. In the State of Ohio, every county Sheriff Department looks the same (black and gold cars, black uniform shirt, grey pants, stetson style hat), they are all regulated by the Buckeye State Sheriff's Association. In the movie the "local sheriff" wears a brown uniform and drives a car with white doors. This is not accurate. The front and back of the car is accurate with the gold stripes, and the license plates on the cars are also accurate, but those are the only parts of the cars/uniforms true to the state of Ohio.