Google page indexing issue, Server error (5xx)

We’ve just received a Server error (5xx) warning from Google about this URL https://www.mcveaghfleming.co.nz/articles/tag/Acknowledgment

The page doesn’t exist, and all pages under articles would be collections generated and be either:
/articles/…
or
/article-tags/…

So I don’t understand where this url would be coming from
https://www.mcveaghfleming.co.nz/articles/tag/Acknowledgment
the path ‘/articles/tag/’ doesn’t exist in the hierarchy.

Has anybody had anything similar from Google Console, or understand why this may have happened?

I’m going to create a redirect to sort things out but I’m perplexed as to why the URL exists, it seems nonsensical to me.

Grant