Character mistake: When Beth and her mother discuss the agent's fee of 15%, Beth says it is $49.54. However the prize money was $500, the expenses were $172.30, which leaves them $327.70. 15% of $327.70 equals $49.16. (00:10:00)
Factual error: The car accident scene takes place in Kentucky but the state troopers are wearing the uniforms of Pennsylvania state troopers evident by the distinctive keystone arm badge.
Continuity mistake: Beltik rolls up his right-hand sleeve. Says, "Hell no" to the offer of a draw. Other side tips King. When they shake hands, Beltik's sleeve is back down, then back up.
Factual error: The year is 1967 but the song Classical Gas wasn't out until 1968. Same is true for the song Venus which wasn't released until 1969.
Character mistake: The American flag in the gymnasium of Beth's first competition is hung incorrectly. The correct way to hang the flag, if hanging it vertically, is to display the stars in field of blue in upper left corner, not as displayed in the film. (00:31:00)
Continuity mistake: The lady asks her for three packs of Chesterfields, at the store, the shopkeeper gives her just one pack, and she can be seen holding and walking with just one pack. When she returns to the house, she puts three packs of Chesterfields on the kitchen counter. (00:24:37 - 00:26:11)
Adjournment - S1-E6
Character mistake: When Beth is asked to solve a chess puzzle, she answers, "King to Queen 7." The white King is nowhere near the 7th rank. (00:10:38)
Suggested correction: You're looking at the board the wrong way. When he sets it up, he's using his side as the white side so Beth is sitting on the black side. So the white king is on Q6. Since the question is about white winning, she's playing as white and using white's notation, just from the opposite seating position.
Factual error: Just before Annette Packer and Beth begin, the host pumps some water out of a cooler. I don't recall seeing that kind of dispenser - usually for coffee or hot water - until many years later.
Character mistake: During Beth's final match against Borgov, the position she stops to think about features her Queen on D3 and Bishop on E3; however, the staff member operating the spectator display board has these pieces on C3 and D3 respectively, and since this places her dark-squared Bishop on a light square, it's particularly confusing as to how he would have made such an error. (00:55:00)
Factual error: At the 1966 Chess Championship held in Las Vegas they show a brown 1967 Mustang.
Character mistake: When it shows young Beth with her mother in the car, she has blue eyes. Her character is meant to have brown eyes.
Adjournment - S1-E6
Factual error: The song in the car when they were heading to New York was released in 1979, but this scene is set in 1967. (00:01:04)
Suggested correction: The song playing is "Stop Your Sobbing" by The Kinks, which was released in 1964. What you're talking about is The Pretender's cover version from 1979, but that's not the version heard.
Middle Game - S1-E4
Other mistake: Beth walks into the pool and the letters are mirrored. (00:19:53)
Suggested correction: If you're talking about the "Aztec Palace" sign, it's not a mistake. The sign is on top of the building in bright lights so that if you're facing the front of the building, the sign is the correct way. But since there's nothing on the back of the sign, if you look at it from behind (such as in this shot), the letters would be backwards.
Continuity mistake: The first time Beth plays Beltik she starts the game as black but finishes the game as white.
Suggested correction: Maybe you're thinking of a different scene. When she's waiting for Beltik, she's playing white. You even see she's moved her pawn and it's white. When Beltik shows, he moves his black pawn.