Just returned from our first trip in our new 5er. Had a great time and weather was sunny all weekend. The learning curve that accompanied going from a pop-up to a 5er wasn't that bad. The only problem: I noticed water leaking into the front pass thru storage just below the shower. The drain line is visable with no leaks. The water is running down between the luan board and the exterior fiberglass. I'm thinking that the water is getting through where the base of the shower meets the shower walls. Anyway, calling the dealer tomorrow, as it is still under warranty, the only problem is that the dealer I bought it from is 3 hours away and the local dealer has the attitude "if you didn't buy it here, we can't get to it for three months." It's the little surprises in life that keep it interesting.
Might also be at the connections on the shower head. There should be an access panel on the other side of the shower wall that you can remove and check.
The floor under my entertainment system was getting wet, and a close inspection showed the supply line to the shower penetrating the wall. At the point of penetration they had connected 2 lines, and the connection was half in half out of the side wall...obviously road vibrations worked the connection backwards and presto...water leak.
Whether your a Gazelle or a Lion, when the sun comes up...you better be running.