Following a major overhaul, the BBF / DIPF archives (Research Library for the History of Education (Q856552)) presented a new version of it's website and database in May 2017. As a result of this, the old identifiers of the personnel files are obsolete, and the old Links don't work anymore. I've contacted the staff on May 22 and quickly got in touch with a very helpful employee who told me about the overhaul and the new system. We hope, with the help of the currently overworked BBF technicians, to get the issue fixed as soon as possible.
On the plus side: The BBF is glad that we are using their database as a reference, and are interested in further cooperation. Jonathan Groß (talk) 09:48, 1 June 2017 (UTC)
The BBF staff has painstakingly created a list matching Wikidata Items, old BBF IDs, and new BBF IDs. Avalailable here. Jonathan Groß (talk) 08:21, 30 June 2017 (UTC)