pll_the_languages missing translated category

Hi,
I have a strange issue, potentially a bug, but I’m unsure how it could be.

The provided link to a category page for a custom post type allows for switching to the 2nd language, but from the 2nd language page, the switch back to the original language redirects to the front page.

The links to the translated page are generated through pll_the_languages(). For your reference, I have the data returned from that function for each page through print_r() in a hidden <pre> tag immediately under the </header> tag.

I assumed that there was something wrong with the connection between the pages in the database, I cleared the connection between the categories and reestablished it, but no go. Other category pages of this post type do not seem to have this issue.

The page I need help with: [log in to see the link]