As there seems to exist no solution for the Dropbox problems we decided after some reflection to go back to ADrive. ADrive seems to have almost no limitations to downloads. It allows up to 1.000 downloads at the same time which will probably never be reached on our blog. Let's hope things work now without any problems. Step by step we will transfer all Dropbox links to ADrive. We did already the two most recent ones and will still this evening post a new entry.