Rewrite rules not working for one specific child taxonomy

I created a hierarchical taxonomy called County, and set up three parent taxonomies, each with a child taxonomy. When these are selected, they get appended to the permalink for the associated posts according to some redirect rules that I wrote so that I have specific urls that I can use to easily display filtered search results.

My problem is that for literally just one of these child taxonomies, if I select both the parent and child, the permalink breaks, only showing the parent taxonomy in it. I can still manually navigate to the correct permalink, but the permalink given to the post will be incorrect when viewed from the admin panel or in search results, and give a 404 error when clicked.

This is literally just happening for one specific child taxonomy. Every other parent/child taxonomy pair has no issues. I even tried creating a test taxonomy under the parent taxonomy of the broken child taxonomy, and that pair worked as well.

I know this is kind of vague, but hopefully my explanation makes sense and someone can nudge me in the right direction on how to solve this! I don’t even know where to begin.

I did check the tables associated with taxonomy in the database to see if I could find any duplicates, but didn’t find anything out of the ordinary. I don’t think it could be a problem with how I registered my post types or my taxonomy, because as mentioned it’s working for everything except one specific child taxonomy.