When you download a route from the DLS, it's dependencies are automatically downloaded as well. Only the dependencies that you do NOT have installed will be downloaded with the route. That's no guarantee that those dependencies will be up to date, or without faults. I'm not sure if there is a limit on faulty content that will cause a route to not load, or if one single faulty asset will prevent loading, but that's more than likely your problem.
Having you been updating your content and fixing content that is faulty?
If you download a route from another website, then you're usually on your own to find all the dependencies.