I'm already looking for hours, but I honestly think I oversee something simple. Here is the problem:

we have a website with the following structure:

site.nl/blog/categorynames/postname

So in this example:

site.nl/blog/red/flowers/

All working fine, except for 1 certain category (red) Everytime you go to a post within this category or the category itself, it's just showing the archive page. So the URL is correct (it shows site.nl/blog/red/flowers) but I see the same page as site.nl/blog/

If I:

• change the category the post is shown (from "red" to "blue")
• change the slug of certain category (from "red" to ("red-2") the post is shown

What I already tried:

• there was a tag with the same slug, I deleted that one
• Permalinks refresh, didnt make a change