Goodbye Mrs. Slocombe - S10-E1
Audio problem: At the end when Capt. Peacock comes onto the floor in his maintenance garb, Mr. Harman points him to a spot on the floor and tells him to mop it up. In the initial shot Harman is indeed telling him, but when the camera cuts to another angle Harman is visible and still talking but his lips aren't moving.
Camping In - S1-E4
Other mistake: The episode takes place on March 2nd, 1973 (date of the newspaper shown by Mr. Mash), but in Mr. Rumbold's office the sale chart for the month of March is already fully filled up.
Revealing mistake: When Captain Peacock goes behind the curtain to the hall way to Mr Rumbold's office, you can see that the sets are right next to each other and the other actors are waiting in there for the next scene.
Continuity mistake: Mrs Slocombe is showing a bride a veil and puts it on the counter, but in the next shot she is still holding it and puts it down again.
Continuity mistake: The set up of the canteen changes from episode to episode. It is never the same way twice.
The Hold Up - S10-E3
Continuity mistake: When the robbers have nodded off and Mr. Spooner and Cpt. Peacock cut themselves out of the rope tying them to the cabinet, a clock outside is sounding the hour; if one listens it chimes nine times. But minutes later, after the rest of the group have come in and they make the call to Mr. Rumbold, the latter exclaims "It's after midnight." upon answering the phone even though less than ten minutes have passed.
Revealing mistake: At the beginning of the Scottish dance when Captain Peacock is demonstrating the sharpness of the swords, he first cuts through the center of a newspaper page held up by Mr. Spooner. However, you can see that, just before the sword makes contact, Spooner actually tears the paper apart down the middle.
Cold Comfort - S2-E2
Revealing mistake: In the very beginning of the episode you can see Mr. Grainger sitting in a chair to the very far left, with his head down, waiting for his cue to walk-on.
The Hold Up - S10-E3
Plot hole: When the robbers come onto the floor and go into Mr. Rumbold's office, the staff suggests calling the police, only to be told by Mr. Harman that the only outside line is in Rumbold's office. This, despite the fact that there have been numerous occasions throughout the series where characters made and received personal calls on the department phones (Mrs. Slocombe calling her cat, Mr. Humphries calling his mother, etc).
A Change Is as Good as a Rest - S5-E2
Visible crew/equipment: In the opening scene in the board room when Mr. Lucas is commenting on how Mrs. Slocombe is "big in the south," you can see the shadow of a boom mike floating back and forth across the table.
Audio problem: When Young Mr. Grace arrives, the sound department misses his first "Good Morning", which is audible only very faintly towards the end. (00:15:35)
Continuity mistake: Sometimes Mrs. Slocombe has discretion over both inventory and displays and what they will and will not sell in the ladies department, other times its Captain Peacock, Mr. Rumboldt or others that have the final say.
Revealing mistake: When Mr. Lucas goes to "knee" the pair of pants, the pants already have the hole in them, and his knee doesn't rip anything.
Cold Comfort - S2-E2
Other mistake: At the very beginning you can see a girl in the background with long hair, pausing to speak and gesture to someone off stage, before she removes the sheet draped over the counter.
Continuity mistake: Normally the windows in Mr Rumbold's office are latch swing open style, but when the staff are viewing the parade they are plainer push up windows.
Factual error: Mrs Slocombe's cat gives birth, but the kittens shown at the end are way older than ones who are supposed to have been born just moments before.
Revealing mistake: The cake the groom's father has is treated as if its real, but when smashed over Mr. Grainger's head it's obviously Styrofoam and hollow.
Friends and Neighbours - S10-E6
Revealing mistake: When Mrs. Slocombe's cat is supposed to be under the hat and "eats" the clockwork mouse, it is clear that it's a machine. This is most obvious when the hat spits out the mouse and slightly rises up in the front, which shows the wheels.
Continuity mistake: Mrs Slocombe arrives with her hair in disarray, but once she walks away she only has time to put her coat away before she returns, by that time her hair is neat with no evidence of it being messy. She had to have returned quickly to hear Mr Humphries' story as she comments on it shortly after.
Continuity mistake: In the ruined photo taken of Old Mr. Grace and his nurse and secretary, the secretary is looking away from the camera and her leg is raised. However, in the scene preceding, she was looking at the camera and raised her leg after the flash went off. Also in the photo, both of Mr. Humphries' feet are in the air, though one was on the floor when the picture was taken.
Answer: That wasn't possible in 1972. Until recently squatting was a civil offence in the UK, not a criminal one, and removing squatters was a complex and time consuming business.