Revealing mistake: When Rodney is asking Del if he thinks the bathroom is haunted, you can see stage lights in his spoon. (00:10:20)
Continuity mistake: Near the start when Albert is plating up the takeaway, you see him beginning to remove the lid from the takeaway. In the next shot however, the lid is completely off. The change in shot is immediate and there is no way that Albert could have moved it in that time.
Continuity mistake: When Del puts the painkillers in his drink, it changes to a lighter colour. Yet when he picks it up off the TV a few minutes later, it is back to it's normal colour.
Chosen answer: An apparent long string of illnesses.