Comment 3 for bug 1900637

Since it doesn't seem like this is reproducible, my guess is it was a matter of what is ultimately a temporary issue. A mirror sync would be syncing the archive mirror (in Australia in your case) to the canonical/Canonical ☺ mirror. If getting all the index files happened before the sync, but a package that had changed during the sync was being downloaded after the sync, then we'd have this problem. Repeating the process almost immediately should yield positive results.