Ashenden's resignation letter changes between scenes. The first time we see it, it reads: "Now that I have resigned / if you want a successor for / me I can give you the / name of a good reliable butcher" When Carrington later looks at it and cuts it up, it reads: "Now that I have resigned / if you want a successor / for me I can give you / the name of a good / reliable butcher"
The General (Peter Lorre) drops his hat in the church and then he runs upstairs together with Edgar Brodie (John Gielgud). When they get there he has his hat on again.
Dates given in the story are out of sequence. After starting "May 10, 1916" (title), a telegram received later appears to be dated "3/4/16". A newspaper near the end of the film is dated "Tuesday, September 21, 1916," when that date actually occurred on a Thursday. Afterwards a postcard bears the date of "April 2."
When the man with one arm is trying to move the coffin, the flag is draped over his right shoulder but in the next close-up, it is only covering his forearm.
When you first see the hotel bathroom, the toilet roll is held on its holder with the end hanging at the back of the toilet roll hanger. When 'The General', however, goes on a strop for not having a wife 'issued' to him, the toilet roll is hanging with the end on the front of the toilet roll holder.
A newspaper gives the date as Thursday May 10, 1916. In actuality, May 10, 1916 was a Wednesday.
Although the film is set in 1916, fashion, hairstyles and set decoration are contemporary to 1936.