This episode shows Ducky and Angus meeting up (this would be after Angus and Maggie got married). But in Season 12 Episode 3 (So It Goes), Ducky states that the last time he saw Angus was at his (Ducky's) going away party, when he knocked out Angus' two front teeth. Which would not have been the case, because of the flashbacks in this episode.
When Jake and Ellie are talking in the parking garage, Jake is wearing his glasses as seen over Ellie's shoulder, but is not wearing his glasses as seen over Jake's shoulder.
When Mr. Palmer is explaining that he doesn't know where Dr. Mallard is, he says that Dr. Mallard told him he was going to pick up dry cleaning. But earlier, when Dr. Mallard left the lab, he brushed past Mr. Palmer without saying anything at all.
In a flashback scene set in England, as the the young Dr Mallard enters the hospital he says he was ordered to report to the ER. This is an American term; British hospitals do not have ERs. The correct term at the time the scene is set would have been "casualty".
A common British term is Accident and Emergency A&E.
Ducky's father tells him that he has been served with divorce papers and his wife is taking Nicholas. A divorce in the UK would require a decree nisi first, then a decree absolute, and isn't just a foregone conclusion. Custody would not be automatically given to the mother (although she would generally be given preference) and taking the child out of the country without the permission of either the court or the father would be illegal.
When Ducky gives his younger brother his Christmas present, he refers to the steam engine to be a 4-4-6-8 steam locomotive named Mallard. Gresley's A4 locomotives are actual 4-6-2 engines (refers to wheel arrangement), with Mallard having been assigned the number 4468.
The nurse at the home where Nicholas is living states that he has no recall of his past life and hasn't had for years. While it is obvious that this is not the case by the letter to Dr. Mallard, she should and would know that the oldest memories are the ones that are the last to go with Alzeimer's patients. Nicholas should therefore instantly have recognized the Mallard steam engine given to him by Ducky.
The staged suicide victim's death was 12 hours earlier, yet it was stated that chlorinated water from the lungs was matched to the pool water. However, the chlorine in the water would have been absorbed into the lung tissue very rapidly, and there would have not been any remaining 12 hours later.
In scene with young Dr. Mallard and his young brother Dr. Mallard's right epaulet is shown above his collar, which is incorrect. The left epaulet is fine.
The British-born actor who plays young Ducky has an English accent, with no trace of the mild Scottish burr of Ducky or the actor who plays him, who is originally from Glasgow.
In last scene with young Dr. Mallard his right epaulet is shown above his collar, which is incorrect. The left epaulet is fine.
When young Ducky is seen in uniform, he is wearing two pips, which is the rank of 2nd Lieutenant. A fully qualified surgeon serving in the RAMC would be at least a Captain.
When young Ducky is talking on line 4 there is a wall mounted phone that's a style that wasn't used in the UK at all.
British hospitals didn't use phones that have extensions on them i.e. line 4 calls would be managed through a switch board operator.
When they go into the pub, Nicholas asks Ducky if he can increase his debt from £10 to £11 as he wants to play on the pinball machine. Ducky gives him a £1 coin and he runs to the machine and puts it in. Not only was the £1 coin not minted until February 1983, at the time the scene was set, which we know was 40 years ago, it would only have cost 10 pence to play pinball.
The 'Flight of the Mallard' train set given by Ducky as a Christmas present to his brother was actually released in 2015 to celebrate the 75th anniversary since Mallard's world speed record. In addition the Hornby branding is too new - it would have been known as Triang Hornby or Hornby Railways.
Donald 'Ducky' Mallard is seen giving his younger brother a 'Snickers' bar, in the UK this would have been known as a Marathon bar until it changed to snickers in 1990.
The ticket to Albania was from 1973 yet the pinball machine in the pub prior to that was a Bally Delta Queen, manufactured in July of 1974.
In the pub, the drinks are served in straight glasses. These didn't become commonplace in English pubs until the late 1980s, traditional handled pint glasses would have been used.