During the conversation between Mr. Hamilton and Sybil after "Is your husband all right?" she takes out a pack of cigarettes, and one second later, after a shot of Mr. Hamilton, it's smoking in her hand.
When Basil re-emerges from the kitchen wearing the hat, carrying the wine, and about to read aloud the "letter from the chef", there is an obvious scene break. Before reading the letter, Basil pours wine into Harry Hamilton's glass only. However, when he starts to read the letter the wine bottle switches from Basil's hand to the table and both wine glasses are now full.
According to the dialogue, The Hamiltons arrived at the hotel by car, having driven five hours from London. However, when Harry Hamilton decides to make an early departure following the dinner fiasco, he calls for a taxi. If the couple arrived by a car they drove themselves, then presumably it would still be parked outside. Calling for a taxi to leave the hotel doesn't make sense.
When Basil is checking in the Hamiltons, the boom mic appears several times at the top of the frame.
Sybil tells the guests that the chef came from Dorchester, around 14 miles from the hotel. The hotel is in Torquay, approximately 75 miles from Dorchester.
Basil says "hand waited on hand and foot" at one point.
Basil tells Sybil about giving his regards to Polly and Manuel, but forgets to mention Terry.
Basil claims that he can't afford to pay Terry two hours' overtime, but the £20 that Mr Hamilton gave him would've been more than enough to do so (around £170 in 2020s money).