When Morse tells Lewis about his childhood, he says his mother died when he was 15. But in the series Endeavour, Morse tells Thursday he was 10 when his mother died.
At the start, when the girls are picked up from the rave, the car that pulls up to collect them is clearly a Ford Escort. When it cuts to the scene inside the car and it pulls away, it's turned into a Datsun Stanza.
At one point Strange says to Morse 'I can't imagine you young", however they are seen working together in Endeavour, when they were both young.
The sergeant on the drugs squad shows Morse the drugs that she confiscated from the dealer after booking him in at the police station. The drugs are in small plastic bags, as would be necessary for the dealer to carry them around, but these are not police evidence bags. This means that the evidence has not been sealed and would be inadmissible in court, even at the time when the episode was set.