This is the result of a long discussion on the Katello forums: https://community.theforeman.org/t/katello-4-1-2-1-404-error-through-content-proxy-due-to-incorrect-location-href/24812/27 TL;DR if you sync a repository on-demand multiple times against different repos, only the first set of RemoteArtifacts is saved. If the layout of the repository changes or the repository disappears, all of these URLs get broken, and the RemoteArtifacts are thus broken even if they were supposed to have multiple different potential sources. This can be reproduced by syncing a single repository, publishing + distributing, changing the layout of that repository, URL to its own distribution, and resyncing. Only the original RemoteArtifact will exist and the new ones will not. A script is attached to demonstrate this (if you look in the DB afterwards) exist.