this can be closed. After several backups and restores, it is quite likely, that a mismatch of versions has happened. I had a deeper look and found some files with versions pre-2.5. 
Meanwhile I updated to 2.7, and all works as expected. No more issues with "too high S-Value.".
Meanwhile I updated to 2.7, and all works as expected. No more issues with "too high S-Value.".
Luckily you found the error
You can close the topic yourself, open the original post, expand the additional options, select the "lock topic" box