Asgard's Wrath download/installation problems (solved)

I have experienced problems with downloading Asgard's Wrath as many others. The suggestions I read online are either outdated or do not work. I know now when the issue occurs and how to avoid it.

Usually you can pause and continue a download. With Asgard's Wrath you can do that, too, but you cannot do that during the endphase of the download. Otherwise the download stops and the already downloaded files get deleted and you have to start over.

So make sure, that you download the last ~30GB without interruption. Do not pause the download and make sure your internet connction is stable. If you have DSL you usually have a disconnect every 24 hours. Make sure this does not happen during the last part of the download.