Interesting we had very good luck with the maps but were mostly in Germany, Austria, and France. To the point that we ended up on some very narrow back roads to get around a road diversion. It went very smoothly. I should also note that we supplemented the navigation with other maps, actually Google maps. Even as an American I have never had an issue with languages - and would expect anyone going to a foreign country to do their homework beforehand. So I am not sure how sensitive they should be.
That said, given you dropped the car back off in Munich, like most I assume you went directly to the airport rather than talk to the folks at BMW Welt. Whom I found to be supper helpful and attentive.
I will note that when we initially wanted to drop our car off that it was a German holiday. When we returned I sent a note to
BMWEuropeanDelivery@bmwna.com and suggested some changes to their website regarding holidays. They took those suggestions and made some changes. Was this the email that you sent a message?
Edit to add: Did you check the version of the maps? I would guess they were BMW's version of the 2013 maps.