Factual error: Lucas is constantly twirling the rifle after rapid firing a few shots. Since the cocking ring is set on semi-automatic, the rifle should fire as it comes around.
Suggested correction: He twirls the rifle in the opening of the show, after he's just emptied it completely.
The original comment doesn't state the beginning of the show. This does happen throughout the series.
Factual error: There is an intercom system in the library that is used by Derek (and at the end, Edward). They try pushing down the buttons to talk (which is normal for intercoms), but then each time, we are hearing Ricky and his grandfather's conversation from inside the car that's outside without using the intercom connected to the house. In the 80s, a house intercom system would not pick up a conversation in a parked car outside.
Factual error: There's an exhibit in the Smithsonian Institute that shows Benedict Arnold, William Demont, and Major John Andre labeled as Famous American Traitors. One problem, Andre wasn't a traitor to America as he was a British officer to whom Benedict Arnold arranged to surrender West Point to during the war.
Factual error: About 1/3 through the show, Greg has to talk to Marcia and asks Peter to leave. On the way out Peter stops to start recording on the tape recorder. He only pushes the play button. He would have had to push the red record and play button to record their conversation.
Factual error: Shannon asks Leah if she knows what happened to Tom Smith - she replies that Tom has gone to university, but in the previous series Tom was only in his first year of sixth form, and it takes at least two years in the sixth form to study for the A levels required for a university place.
Suggested correction: Although normally A-levels are taken after 2 years, it is possible (and often done) to study them in one year.
Factual error: Aunt Petunia says that the chalice was first seen in the Stone Age, and sends Paul and Barry back to where Stonehenge is just being completed. However, the Stone Age actually ended in around 3300 BC. Stonehenge is believed to have been constructed in around 2500 BC, which was the Bronze Age.