Basil picks up Lord Melbury's cases outside the hotel. When he brings them inside the cases have swapped hands.
When Basil is told that the Morrises are leaving, he goes running after them and his hair is messy. When he's outside his hair is neatly combed back. When he comes back into the hotel it's messy again.
When Polly rings the bell at reception to get Basil's attention, he lays the cases of coins on the counter. Polly finally convinces him to go into the office to talk, leaving the cases on the counter. When they return to meet the Morrises, the cases are gone.
Basil keeps getting distracted from hanging the picture on the wall. Throughout, the picture clearly has no glass covering it, yet at the end when Basil smashes the picture on the ground there is a distinct sound of glass breaking.
When Basil asks if Melbury has any bricks to deposit, Melbury runs off screen where there is presumably a wall. In the same scene, he comes out of the bar.
Basil is seen filling in a football pools coupon dated Saturday 26 January 1974 from the London based Copes football pools company, which would be impossible as Danny Brown's surveillance car has a tax disc expiring March 1975, meaning it could not be issued or displayed until 1 April 1974.
When Basil slams the door after announcing that several visitors have to leave immediately, the wall the door was on wobbled, indicating it was a set wall.
The doors on multiple episodes do don't shut or lock so they open again.
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 and the reflection of the studio lights are visible in the picture above the drawing room door.
Later, when Basil says, "May I introduce you to your wife?" John Cleese meant to say "My wife" but he was distracted as he explains in his commentary on the DVD.