Thanks for the tip. I contacted them and they were willing to do it.
But since I live a bit remote the freight costs were depressing...
Found some advice on a German site, and too a deep breath and cut mine open.
Seems it was the same soldering issue as the german guy had, so now it seems to work fine.
Like to German site here, in the post there is a picture showing where he cut it open.
Chrysler - Dodge - Jeep - Auto - Forum | Chrysler Crossfire - Forum | 2) Roadster 3.Bremsleuchte defekt
There are two printed circuit boards inside (one right, one left). The left one is provided with voltage and ground via two cables from the right board, where the connector goes.
I re-soldered these two connecting cables and then it worked.
:-)