If you recently enabled the "Restrict document roots to public_html" feature in WHM's tweak settings menu, you might cause an issue with your backups created prior to that change. Problem is, your backups created with addon domains inside the public_html, now when you try to restore an account restore will fail as the restorepkg is not allowed to create addon domains inside public_html
The problem is only affecting accounts created during the overlapping time, that is when you enable the feature through WHM, until you reached your backup rotation limit. For these backups, the only workaround is disabling this option in WHM tweak settings, and restore again.