When Miss Lemon arrives at the hospital to check birth records for Poirot, she gets out of the car wearing a red dress with a white sweater. Moments later as she's entering the Records Office, she's wearing a blue dress with white sweater. In the next shot, it shows her going through the Records books and she's back in the red dress again. In her next scene she arrives back to give Poirot the info she's found and she's once again back in the blue dress.
The the young soldier Peter Baker arrives on home on leave he's wearing brown socks when he jumps out of the truck and green socks when he greets him mother in the front hall of the house.
The man says that few people would be denied rights based on race creed or gender. Gender was not used ti describe sex until it was proposed by John Money a disgraced researcher in 1965. Prior to that people would have used sex which was and still is the correct term.
When Hastings is driving Poirot to the Cambridge Union, they drive east along Trinity Lane, and turn right (ie south) into Trinity Street, and continue south past Caius College. In the next shot they are getting out of the car on St John's Street, just where it runs into Trinity Street. The car is still facing south, but has somehow travelled 200 metres north since the previous shot.
Also they could only have been driving along St John's Street in the direction away from the Cambridge Union to reach that point.