I have had similar experiences with automatic downloads and now go to the site to download an install manually.
The problem, I think, is one of priority. Automatic download seems to operate on the current usage of your PC and what you want to download/read/etc. and, perhaps, the Microsoft site loading. So if you simply rely on the automatic system you may well find that downloading is much slower.
I`m certain those with more technical knowledge will correct this if it`s wrong??