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
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.