Continuity mistake: When Del asks Rodney why Denzil lost his job, there is no sign of Denzil or anyone else behind Del. When Del turns round, the market is packed and Denzil has appeared from nowhere. (00:09:25)
Continuity mistake: In series 4 episode 2, we see Grandad's grave. The scenery is sparse, no trees or bushes. In this episode Del is at their mum's and points to Grandad's grave. There are now massive trees and bushes.
Chosen answer: An apparent long string of illnesses.