When Captain Tyler is drilling the 2 Guardsmen, he orders the Men to "turn to the left in three's" when there is only two of them, the order should have been "Turn to the left in line, Left Turn" Captain Tyler them orders the Men to "by the right quick march" how can they march by the right when again, there is only two of them, Captain Tyler should have ordered, "Advance in single file, slow March".
When the Senior British Officer on arrival at Colditz meets the Commandant in his Office the date on the calendar is Tuesday 17 May. There were no 17 May dates which fell on a Tuesday in World War 2.
When the Frenchman is on the tiled roof of the prison, one can clearly see that the 'tiles' move and are compressed by his weight, notably his feet. The entire section is covered in a contoured printed rubber sheet to simulate roof tiles. This is obviously to prevent the actor from slipping on the steeply sloping section of roof.
Christopher Rhodes is listed as "Chistopher Rhodes" in the opening credits.
According to the calendar on the Kommandant's desk during his interview with Colonel Richmond about moving the Polish prisoner, the date is "Dienstag Oktober 4" (Tuesday October 4). October 4 did not fall on a Tuesday at all during WW2, although it did in 1955, the year of the film's release.