seo – Why is the "user-specified canonical" URL between "GOOGLE INDEX" and "LIVE TEST" different in the Google Search Console?

I'm working on a site that has recently seen a drop in search traffic. When digging through, we noticed that our latest content is not indexed. When I check some of the URLs in the Google Search Console for new content, the reason for the non-indexing will be "Duplicate non-canonical URL".

From there, I see several cases where, using the URL Verification Tool, the User-Declared Canonical URL displays a different URL (for a completely different and non-contiguous content than years ago). Most curiously, when using the "TEST LIVE LINK" button, the "user-declared canonical" displays the correct URL.

I can verify that the canonical tags in the content are correct. I've confirmed that both in Chrome and via curl (just in case Javascript has changed some front versions of the rel = "canonical" declaration).

Why is the "user-declared canonical" tab different between "GOOGLE INDEX" and "LIVE TEST" in Google Search Console?