Gourmet Night (a.k.a. Gourmet's Paradise) - S1-E5
Audio problem: When Basil is pretending to be a duck and quacking, you can tell it is false because the quacking stops a second after Basil stops pretending to quack.
The Kipper and the Corpse (a.k.a. Death) - S2-E4
Character mistake: When Sybil is telling Basil that the two men and the woman are coming to collect Mr Leeman but he's already pronounced dead, she tells her husband that they are coming to collect him "at lunchtime". However, his colleagues told Mr Leeman they'd collect him at 9:30 and not lunchtime.
The Germans - S1-E6
Visible crew/equipment: After Basil has turned the fire alarm off, a boom mic is very clear in the top corner of the screen.
The Kipper and the Corpse (a.k.a. Death) - S2-E4
Revealing mistake: Just after Polly comes down to to the kitchen to tell Sybil that Mr Leeman's dead and they leave, Basil wanders back in, to learn the news. Watch the wall on the right on the staircase when Basil shoves past Sybil on the stairs. The wall shakes so much at that point it's virtually impossible to miss.
Audio problem: Throughout the episode the picture Basil is distracted from putting up has no glass covering on it. However, when he smashes it at the end you can hear the distinct sound of glass breaking. (00:29:35)
The Builders - S1-E2
Revealing mistake: In the scene where Polly brings Mr O'Reilly a cup of tea, it is obvious on several occasions that there is nothing at all in the cup. Not only does he hold it in such a way that you can see inside, but when Basil snatches it away nothing spills out.
Deliberate mistake: In nearly all the episodes that the front door of the hotel is open we see a painted board that is meant to be bushes or something outside. Yet whenever we see scenes from the outside of the hotel there is no sign of any trees or bushes.
The Builders - S1-E2
Continuity mistake: Towards the end of the episode, a couple of scenes before Mr Stubbs arrives, we see Basil start up the tape player prior to hiding in the kitchen. The garden gnome on the desk is right next to the tape player at this point. When Sybil turns the tape off the player has rotated 45 degrees or so (despite nobody else having come into reception in the intervening time) and the gnome is now further along the desk towards the camera as we look on the wide shot. The gnome in the next shot is seen beside the checking-in book when Basil wanders out of and back into the office a couple of scenes later, yet when Mr Stubbs is asking about the lintel for the new door shortly after that and we see Sybil writing in the book, the gnome has moved out of shot altogether.
Visible crew/equipment: When the bald hotel guest asks Basil for his drinks and slams his hand on the table, in the next shot a boom mic can be seen briefly as it is pulled away. (00:24:05)
Visible crew/equipment: Near the start of the episode, after the guest has told Basil that he will only be staying until Sunday, Basil walks from the dining room to the office, and the shadow of the camera following Basil can be seen in the reflection of the studio lights in the picture above the Drawing Room door. (00:04:45)
The Kipper and the Corpse (a.k.a. Death) - S2-E4
Visible crew/equipment: In the kitchen scene with Basil, Sybil and chef, Basil says, "Would you believe it, I give him his breakfast, I take it all the way upstairs." At this point, the shadow of a boom microphone on the wall to the right is visible.
The Kipper and the Corpse (a.k.a. Death) - S2-E4
Revealing mistake: When Basil, Manuel and Polly are trying to hide Mr. Leeman from the other guests, they put him in a cupboard. While they are talking to the people staying in the room, Mr. Leeman's hand comes out of the cupboard. Watch carefully, and you can see the actor opening the door from the inside, and then putting his arm down, making him look like the corpse.
Revealing mistake: Whenever somebody closes a door, leans against a wall, or goes up/down the stairs and brushes against the wall, it wobbles, revealing that the walls are lightweight stand-up props.
Communication Problems (a.k.a. Theft) - S2-E1
Visible crew/equipment: In the scene where Polly tells Manuel to go and fetch toilet paper for Mrs Richards, the boom microphone shows up at the top left for a few seconds.
Visible crew/equipment: When the Hamiltons arrive, Mrs Hamilton says 'May I introduce my husband.' The boom mic is seen at the top of the screen.
Continuity mistake: When Basil is talking to Mr. Hamilton in the dining room there is smoke coming from the kitchen. The next moment he goes into the kitchen and all the smoke is gone. (00:24:00 - 00:25:00)
The Kipper and the Corpse (a.k.a. Death) - S2-E4
Visible crew/equipment: When Mr. White asks if Basil can clean their room later the boom mike shadow is visible on the door behind Mr. White.
Gourmet Night (a.k.a. Gourmet's Paradise) - S1-E5
Audio problem: When Basil impersonates the duck, the sound effect used continues when his mouth is closed.
Visible crew/equipment: When Basil's trying to persuade Sybil about the woman in the guest's room, the shadow of a boom mic appears on the top wall.
The Kipper and the Corpse (a.k.a. Death) - S2-E4
Continuity mistake: When Basil, Polly and Manuel are trying to hide the body in the cupboard in the guests' bedroom, the door behind them leading to the bathroom mysteriously opens and closes between shots throughout the scene.
Suggested correction: The sound isn't glass as you can see just as he goes to smash the picture there is no glass on the picture.