Someone on Channel 5’s “Great British Model Railway Challenge” first episode commented that in the recent film “Dunkirk”, the characters boarded a 1960s train.
Sorry, but that film began to lose me within the first two minutes when our hero walked past an obviously late 20th century building. I think the producers or directors may have been too caught up in the actual location to seek a realistic location.
And today, while clearing up and meticulously filing (yes – I am getting organised) models from my most recent wargame I have “The Cockleshell Heroes” on the TV in the background. A gratuitous and unnecessary* side shot of a German warship clearly bearing a British frigate reference number. Showing the crew wearing German hats a few moments later does not rectify the glaring error.
But while organising my 1:285 and 1:300 scale models I see that I have far too many 1940 Germans representing 1944 types – exactly like most film costume designers.
And I have created Arnhem with British church ruins and Normandy shops. Who am I to criticise?
Incidentally, during a TV advertisement break in the film I was informed that Colgate toothpaste is created by professionals. Well, that’s another worry resolved!
*Gratuitous and unnecessary. Is that tautology? I stand open to correction from fellow pedants.
General Whiskers' semi-historical wanderings 
The Germans wearing 1943 uniforms in 1940, was the biggest turn off for me.
I find that the opposite is generally true in films, particularly those made in Britain during the 20 years following the war.
In films made during WW2, the old WW1 German helmets are the glaring error, but I guess at that time the Germans were not happy to hand over dozens of the contemporary style…
My real gripe is with the producers of the film “Battle of the Bulge”, who claimed in the DVD extras that they scoured Europe for Tiger tanks, but did not mention that instead they used M48s from the US army in a variety of locations from forest to desert. I can almost forgive Chaffees in place of Shermans as a comparative against the pseudo-tigers, but yet another pointless sacrifice of reality for theater (sic) profits, when so many late war Shermans were available at the time.
The soldier’s hair was too long and it was cobblers from there on in.
It is noticable that the length of hair and facial hair forsoldiers in films seems to reflect the perception from the period in which the film was priduced.
Films of the 1960s and 1970s almost invariably had collar-length hair and long sideburns for anyone from 1800 to 1900, and any other period they could get away with.
In the 1950s military films, and several others, reflected the current “National Service” standards of short back and sides plus a bit of extra trimming.
On the othe hand, we have stereotyping. Probably the worst example I have ever seen is the mock hairstyling in “Cromwell” to differentiate Roundheads from Cavaliers, no doubt sourced from the Ladybird books on the period.