There are two clear errors during the JFK assassination sequence.
LBJ and Lady Bird arrive at Parkland Hospital in a black Cadillac limousine sedan. In fact, they were riding in a light colored Lincoln convertible. An American flag covers JFK's coffin when it is removed from the ambulance at Love Field and when Jackie is setting next to it on Air Force One. It was not covered with a flag until it left Bethesda Naval Hospital early the next day.
The "1955" segment opens with LBJ as Senate majority leader, calling White House Chief of Staff Sherman Adams to try to get President Eisenhower to support an effort to censure Senator Joseph McCarthy. In fact, the Senate censured McCarthy in December 1954, when the Republicans still controlled the upper chamber and Johnson was still minority leader.
When LBJ is in Dallas the day before the assassination, he turns on the TV and as he is changing the channel a baseball game is being shown on TV. Baseball season is over in October.
When LBJ goes to the hospital to visit his sick wife and is speaking to Sam Rayburn, there are MasterCard and Visa stickers on the glass door behind him. These credit cards did not exist in the 1940s.