The main problem is the decision to mix past and present. A number of German characters in contemporary France are forced to flee an unnamed enemy. We all know that, in 1940-1941, they were actually fleeing the Nazis. This is no minor point that can be simply written out of the plot. It is the essence of why the book was written, seeing as Seghers was a communist and a Jew. So, we have to buy into the premise of modern-day Germans hiding out from French police for no conceivable reason. Fair enough if this were some dystopian future scenario, except that they are constantly using 1940s objects, like old passports; dependent on 1940s technology, like trains and ships for transportation; and faced with distinctively 1940s problems, like trying to get transit visas through Spain and Portugal. After the initial half hour of getting used to, where you think this slippage back and forth in time might lead to something interesting, it just becomes tedious and pointless.
There is also an annoying attempt to strike a tone of political urgency, without actually taking a stand on anything. This happens because the German fugitives are tenuously linked to characters of Middle Eastern origin who live in Marseille. This forced proximity gives off the slightest whiff of a comparsion between the German exiles of yesteryear and the immigrants and refugees of today. That would be a provocative argument, but it never goes beyond subliminal posturing. By failing to come out and actually say something, the film stops well short of the weighty political intentions of the book.
The three stars are for the generally good production qualities. The film is well shot, edited and acted, though the soundtrack is annoying. It's the screenplay and directing that leave a lot to be desired.