Gunpowder, Treason and Plot - S2-E10
Factual error: The Battle of Monmouth is shown. There are no leaves on the trees even though the battle was fought in June. In fact it was so hot there were more British casualties from the heat than from battle. It looks like it was filmed on a very cold day in autumn.
Men of Blood - S2-E4
Factual error: The show starts out as being November 14th (1777), which was a Friday. However, Abraham tells Ben it's Monday.