When Ben is driving to the military base, he pulls a map from the sun visor and holds it against the steering wheel. In the closeup, he is using his right hand to trace a path along the map. When the angle changes, his right hand is holding the steering wheel.
This leap takes place in 1949 but the newspaper showing Carrie's conviction for manslaughter, which would take place after the episode's events, is dated Sunday August 18, 1940.
Ian says they will triangulate the possible location of the hidden military installation using the encounters that Ben/the sheriff and Carrie/Melanie had with the UFO. That is only 2 data points. Triangulating a position, as the name implies, requires 3 data points.
After Ben and the sheriff have been run off the road by the "UFO", the sheriff retrieves a pump action rifle from his trunk and fires 4 times at the sky, never pumping or reloading between shots.
On at least three separate occasions, Addison casts a shadow. As a hologram, this would not be possible.
The fact that Melanie and Ben were drugged was identified by the unique double-puncture marks on their necks, behind their ears. When Ben is taken to the military base and injected with the drug again, the syringe used to do so has only one needle. Ben and Melanie should reasonably have only a single puncture mark. If the drug somehow needed to be injected twice in close proximity, there's no way it would have left identical markings on both Ben and Melanie, merely similar ones.
This leap takes place in 1949. However, when Ben and the Sheriff are driving down the road (after playing "chicken" with another car), the lines on the road are yellow. Yellow lines were not used in the US until the 1950s.
The Seeburg jukebox in the dining area is from the early 1950s. This leap is in 1949.
A red and blue mailbox is visible outside the diner where Hannah Carson works. Until 1955 all US mailboxes were painted olive-drab green.
The military would not have had to kidnap and drug Ben. They could have just had his bosses at the FBI order him to stop investigating the case.
While talking about how much the world has changed, the waitress tells Ben that someone from 100 years ago would not know what a yo-yo is, and that it would be seen as witchcraft. Yo-yos have existed since at least 500 B.C.
When Ben is questioning Carrie about Melanie having been awake and running in the woods, Carrie swears "on [her] mother's life". Her mother is said to have died of cancer the previous year. She should be swearing on her mother's grave (a common expression), not her mother's life (which no longer exists).