Factual error: When Tom has decided his scout group will have to go for the food and then his look for his son later, they are stood on a green. There is a war memorial dedicated to both World Wars, 1914 - 1918 and 1939 - 1945. That's got to be in Canada, as the USA didn't enter either war until later than those dates. (00:28:00)
Map of the Seven Knights - S5-E10
Factual error: The Czech crime database (which appears to be an official Czech database) is headed 'Czechoslovakia'. Czechoslovakia has not existed since the Czech Republic and Slovakia separated in 1993 and neither country uses the term any more.
Factual error: The frequency which is used to attract the dragon fly is said to be "sub-sonic" and therefore can't be heard by humans, but the exact frequency is stated to be 38.2 Hz. This is well above 20 Hz, the lowest frequency an average human can hear.