We determined that the slug was not stored in postmeta
meta_key _wp_old_slug
.
In a final attempt to find where this slug is stored. I performed a search for the exact phrase of writing
and found a few results. The one of interest was in wp_terms
.
I deleted that entry and then changed the slug of the category to /writing
and it is working. The strange part was that there were no records within wp_terms
that connected the post to the slug.