While Andrea is in bed getting over his broken ankle we can notice there is one bar of the headboard that is missing in some scenes and a comes out of the blue in others for no apparent reason.
After having his portrait drawn by Olga, Andrea walks out with his violin under his arm. Upon arriving back to the sisters' house, he opens the door with both hands and the violin is unseen. Andrea goes upstairs and is heard playing the violin.
When Andrea is peeling potatoes he carves a face in one. When the shot goes back, the face is completely different.
When the Dr. explains to Olga that the tower in the background was built by a man to give himself a place to hide from his wife he points to a structure that was actually a memorial for the HMS Respite, a WWII battleship that sank off Prussia Cove following the war. Given that the film takes place just prior to the war, the structure should not even be there.
Coley is frequently mentioned as a cheap local fish. Locals confirm that coley was pretty much unknown in Cornwall in 1936 - far more likely would be ling or pollack. Additionally, "starry-gazey pie", of which the fish was to be an ingredient, is unique to Mousehole, about 30 miles from the supposed location in the film.
However, Pollachius pollachius is referred to as pollack in both North America and the United Kingdom, while Pollachius virens is usually known as coley in the British Isles (derived from the older name coal fish).
So basically, they are very closely related and interchangeable.
Andrea peels potatoes and bowls the bowling ball left-handed but plays the violin right-handed, as many violinists may do with right-handed instruments, but it seems a bit strange that the other actions are shown as left-handed.
Mains electricity, gas lighting and indoor flush toilets were unlikely to be present in remote village houses in 1936 Cornwall.
When Ursula is sitting on the beach the reflective shine in her modern stockings made of synthetic fiber is not what would be seen in 1936 cotton or woolen hosiery.
Cattle crossing the road have ear tags not used in 1936 England.
While Andrea is playing at the local party, another violin appears in the lower right hand corner and is being played at the same time that Andrea seems to be playing, but there's only one violin heard at the time. Could it be that the "real" violinist was captured on film by accident?
Truro would not be the first choice of "major town" for shopping in 1936. Falmouth or Helston would be more appropriate.
Andrea is not a Polish name - the Polish would be Andrzej.
Andrea's German alternates between the perfect pronunciation of a German native speaker and a heavily accented version more suitable for somebody whose native language is Polish.