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)
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)
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.
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)
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.