I work on a site that has experienced a drop in search traffic lately. On digging into it, we've noticed that our recent content isn't getting indexed. When I check some of the URLs for new content in Google Search Console, they're showing "Duplicate, submitted URL not selected as canonical" as the reason for not being indexed.
From there, I see multiple instances where when I use the URL Inspection tool the "User-declared canonical" URL is showing a different URL (for a completely different and unrelated piece of content from years before). What's especially odd is that when I use the "TEST LIVE LINK" button, the "User-declared canonical" shows the correct URL.
So, why might the "User-declared canonical" differ between the "GOOGLE INDEX" versus "LIVE TEST" tabs in the Google Search Console?