The Tandem sepcialist shop called the "Tandemladen" in Freiburg is no longer a tandem specialist. The shop exists as before and is called only "Die Radgeber" and no longer stocks tandems. Apparently its a business decision partly because the tandems took up too much space (for the revenue I guess), and now they are just a 'normal' bike shop / repairer / workshop. We were there on Wednesday this week and had a chat. I am sure if you had a technical problem they would be one of the best places to go in Baden-Wurttemburg. Not only to they have a stock of spare parts and accessories and do repairs they also allow DIY repairs where they lend out the tools for on-site repairs.