The Kipper and the Corpse (a.k.a. Death) - S2-E4
Revealing mistake: When the characters are in Mr Lehman's room discussing his death, the backdrop outside the window has clear wrinkles and fold marks in it even though it's supposed to look like the outside.
The Germans - S1-E6
Continuity mistake: When Basil is being pursued by the doctor, the left antler on the moose's head on the wall is broken. When the head lands on Manuel, the antler is not broken or limp any longer, and when the Major wraps the head on the snout, the antler breaks and goes limp again.
The Builders - S1-E2
Continuity mistake: When Basil rushes out of the hotel to see Sybil, his shirt is fully buttoned, but when Basil is seen running down the steps, he has one more shirt button undone than when he was inside.
The Builders - S1-E2
Visible crew/equipment: When Polly passes Basil the stapler, a boom mic can be seen lifting up out of shot in the top left corner of the screen.
The Builders - S1-E2
Visible crew/equipment: When Stubbs says to keep the door closed, a boom shadow is seen on the wall by the door. (00:27:20)
The Builders - S1-E2
Revealing mistake: The umbrella Sybil uses to hit O'Reilly and Basil with is padded to protect the actors. (00:23:30)
The Builders - S1-E2
Revealing mistake: Look at the skirting board of the section of wall Basil hits Manuel against. There are black shoe marks on the paint from previous takes where Manuel kicks the board. (00:16:15)
Revealing mistake: When Manuel throws the grapefruit at the other guests, you can see the woman closest to the camera react before Manuel throws it. (00:11:00)
Revealing mistake: When Basil sends the grapefruit flying, we see Polly go through the doors to the kitchen. However, if you look closely at the doors as she goes through you will see just a plain wall. Not the kitchen as is seen in other episodes. (00:11:00)
The Germans - S1-E6
Character mistake: When the first German guest enters reception, he asks Polly, in German, if she would tell him what time lunch is served. She replies in German "at 9am, in five minutes." Which would be a strange time to be serving lunch! Actually her pronunciation of "9" sounds more like the German word for "no", so could be mistaken for "at no time. In 5 minutes."
Suggested correction: He asks what time lunch is being served. Lunch would not be served at 9am, it would be served around midday. Polly's response is "In no time. In 5 minutes" is absolutely correct. She does say "nein", not "neun" but it is not a mistake.