Factual error: Apparently, Han escapes from a prison in Hong Kong. Then why are the guards speaking Mandarin, which is spoken in China and Taiwan? The guards should have been speaking in Cantonese, which is Hong Kong's dialect. This was probably to convenience Jet Li, who speaks Mandarin but probably little Cantonese.
Factual error: The Lancer that gets lost on the train tracks can't come back into Paris the way it did by taking the metro, as the Paris metro is not connected to the railways. Also, if the movie depicts it going out at Trocadéro, the station is on lines 6 and 9. However, the sign to enter the metro shows the station connects with lines 2, 5 and 8 - no such station exists in Paris.
Factual error: When the police are looking at the reflection of a neon sign in the glasses in the picture of the girl, the letters are reversed as you might expect. But the sign is on the glass front wall of the shop, facing the outside. Since the photo was taken inside the shop, the inside view of that sign would have already been reversed, and the reflection should have been the right way round. (00:35:15 - 00:39:40)
Factual error: The scene at the very end of the film where Billy is grassed up by Alex Kingston. I live in Essex so know that you cannot see Ye Old Plough House (the motel) from Southend Sea Front (the phone box).
Suggested correction: The film was set after the Chinese takeover of Hong Kong so the official language of Hong Kong is now Mandarin as it is in the rest of China.
The principal language of Hong Kong is standard Cantonese, spoken by 88.9% of the population at home daily. As an official language, it is used in education, broadcasting, government administration, legislation and judiciary, as well as for daily communication. As a result of its predominance throughout the community, Cantonese is virtually the exclusive language of official discourse at all levels of the executive, legislature and courts of Hong Kong. Mandarin has increased since 97 but still not the official language.
The official language of Hong Kong is "Chinese." Cantonese is a dialect of Chinese, and not a separately set official language of Hong Kong. While many people communicate in their local dialects, it's not unreasonable to assume they could also be communicating in Mandarin, especially government officials, and especially if they are law enforcement. Not a plot hole or a mistake here.