The Sergeant Major that appears with the Colonel just before the "Self Defence Against Fresh Fruit" sketch wears three chevrons on the sleeve his blue T-shirt (not regulation British Army uniform), denoting the lower rank of Sergeant.
At the beginning of the episode, when the "It's" man is thrown off a cliff (quite clearly a dummy) the cut between the point after the man hits the ground (just out of view) and when he starts crawls up to the camera is very obvious; the gravel on the ground suddenly rearranges. Also the two men who throw the dummy off the cliff are visible, this may be unintentional (since the "It's" man is usually alone).
When Brian (Terry Jones) uses an anti-tank rocket launcher, the shield is not mounted correctly.