Ralf, thanks for looking into it, the analysis and the fix.
I still have to fully read and understand it!

Just to recap: my two initial ideas were
a) it possibly be reproduced without a new attribte, just with title or 
something.
b) the use case is to be able to construct all historic values, even if they 
are there very briefly. 

So a change to title from "a" to "b" to "c" would all be in the log and 
history. Now with the defect "b" could have been lost. I hope this is not 
the case with the fix anymore.