How to replace lost jars in Sonatype Nexus repository?

Question

We have a Nexus repo which seems to have suddenly lost some of our common external dependency jars. We're trying to figure out why, and in the meantime we need to get them back so our builds succeed. Some other artifacts for a given dependency are still there (docs jars, sha1, and such).

What are some reasons for the sudden disappearance of our dependencies?

How can we get Nexus to re-download them?

Answer 1

Nexus will automatically redownload any components that are available in external proxy repositories.

And in terms of the components getting lost I suspect some external access to the storage.