The ship, M/V Stockholm, although not yet built (built in 1953), should be sailing under Swedish flag instead of the Norwegian color that she is flying.
In the penultimate scene the supposedly pre-WWII U-boat looks more like a 1960s NATO coastal submarine with discrete cannon and ack-acks mounted on the conning tower instead of one single gun mounted on the deck.
The mentioned Star of David to identify Jews was first introduced to Germany on September 1, 1941, not yet in 1939.