When Sister Catherine is talking to her father in the garden, there are two camera angles used. The angle of the creases of Catherine's headdress changes between shots.
The coat of arms of Causton Comprehensive School (seen in an establishing shot of the school grounds) has the lion facing to sinister, which is exceedingly rare. If a right-handed knight carried such a shield on his left arm, the lion would seem to be running away from the battle.
The Prioress tells DCI Barnaby the quiet hours, which includes 12-2p every day. DCI Barnaby comes to speak to her later on and the clock on the wall shows 12:40pm, but they speak as if there are no quiet hours.
Incorrectly regarded as a goof: The sister states quiet hours are "10am to 12, 2 to 5 in the afternoon and 9 at night until 6 the following morning," so meeting at 12:40 pm would not conflict with quiet hours.
In the cafe where Jones is interviewing Tamsin, 'prosciutto' is written as 'proscuitto' on the wall where different foods are written.
It was not explained what became of the 60,000 pounds paid for the chapel silver.