I'm impressed with the quality of the German translation, so I'm using it at the moment.
What happened in game #2074910 and some before that used Trade Routes/Handelsroute is that the trade route markers don't appear in the area with a player's name, where pirate counters, VP markers etc. are shown. It works in *some* games, but not in others. Now it seems that this not tied to the German language, after some more tries the English game #2075006 also had the same problem.
Maybe this has to do with other counters being shown there. It is just a visual problem, Trade Route works as it should be and the markers are removed from the victory piles when appropriate.