When the nurse is discovered hidden in the bed, she runs up the stairs in her underwear, but when she next appears, both her petticoat and hairstyle are different.
When the nurse who was left tied up in a bed is set free by a colleague, we see that her hands were tied, but not her feet. She would have been able to get up and walk at any time.
Wilfred Hyde White stick an L plate on Joan Sims' back but then suddenly it's gone.
When the Nurse says to Mr Bishop "What a big fuss about such a little thing" - her lips are saying something completely different.