Character mistake: When Grandad collapses, the Doc calls Morwenna's grandfather Mr. Dunwich, which is the surname of one of his patients in this episode. The grandfather has the same surname as Morwenna, which is Newcross.
Don't Let Go - S5-E6
Character mistake: Mr. Coley the janitor climbs up on the roof and Doc Martin follows, but on the roof he keeps calling the janitor Mr. Munston.
Continuity mistake: Dr. Dibbs puts a chair to block the treatment room door, then bails through the window, Doc Martin and her husband go around the house to intercept her, followed by all in the waiting room...yet, when Doc Martin returns to the treatment room to examine a patient's injured arm, the door is miraculously ajar.
Character mistake: Dr Ellingham makes two character mistakes in short succession in this episode. First, in the bedroom scene with all in attendance, he calls Mrs Dunwich 'Mrs Winchelcy'. Then, when attending to Morwenna's Grandfather William in his garden he calls him "Mr Dunwich." Apparently his character name is William Winchelcy and not William Norcross (Morwenna's surname).