AMG rear light R230 rear fog lamp

Hello guys, wanted to ask you about this, on my SL500 I installed the AMG rear lights. As far as everything is OK, however, I had to find out that the rear fog lamp only works on the left side. On the right side no bulb is defective, voltage (mass) is also present, everything is fine. In the extended condition of the rear fog lamp I also gave power to the rear fog lamp for the test and see because it works. Only in built-in condition my SL wants to burn only the left side of the rear fog lamp. I wrote the seller to the rear fog lamp and he answered the following: Rear fog lamp can only work in German traffic because otherwise it can be changed with brake light. Is the right? Who knows it? And how does it look at your rear AMG lights? Greeting