If a user navigates to an artifact then changes project scoping - the URL at the top of the screen changes to display the new project scoping. If that user then copies the URL at the top of the screen and sends it to another user without permission to the new project scope they will receive a red flare error message - even though they have access to the project the artifact is set to.
This functionality is working as designed. The URLs are dynamic for other uses in Rally.
The Copy Link menu in the artifact has an option called "Plain". This will copy the true plain link for this artifact. Please have your users use this Copy Link Menu in the artifact to create the correct link.