Thanks for the hint, harry!
In comparison to the original release of the August updates, two further ones were added by Microsoft with this re-release: KB 2993100 and KB 2993651. The latter one is the security update that solves the actual problem. Because it is downloaded and installed dynamically by WSUS Offline Update, I omitted it from the lists. In the end, 4 packages are added to the lists for the August Update Rollup.
Greetings
Gerby