Has multiple self-referencing hreflang annotations
This means that the URL in question has one or more self-referenced hreflang annotations, that specify different hreflang values - so there is a conflict between the annotations.
Why is this important?
Self-reference hreflang is not actually a mandatory requirement. It appeared in the original recommendations that Google published as they figured it would be easier for users to just copy/paste the same 'hreflang cluster' on all corresponding translation pages.
However, including conflicting self-referenced hreflang may serve to confuse search engines, to the point where they ignore the hreflang instruction entirely.
What does the Hint check?
This Hint will trigger for any URL which has multiple self-referenced hreflang annotations to the same URL, where the annotations do not match.
Examples that trigger this Hint:
Consider the URL: https://example.com/en/page-a/
The Hint would trigger for this URL if it had conflicting self-referenced hreflang;
How do you resolve this issue?
There is no benefit to including multiple self-referenced hreflang, especially if they are conflicting.
To resolve, either manually update the URLs to remove the extraneous self-references, or fix the script that generates the hreflang (depending on how the site is setup). Alternatively, you could remove all instances of self-referenced hreflang, as it is not mandatory.