Include a link to the source code repository of your project, because we really need the context of seeing your templates and partials to be able to help you. It is trivial to do a quick git clone on your repo, then run hugo server in your project, to help you out. On the other hand, recreating your code from screenshots, or sort of guessing at it, is not.
If you can’t share your repository for whatever reason, consider creating a dummy repo that you can share, which reproduces the problem you’re experiencing.
In creating a new site to demo the problem, I actually fixed it by discovering that the issues was caused by a missing title attribute in the front matter of _index.md in the /posts folder
Adding the following to the file
---
title: Posts
---
fixed the issue.
The demo site that shows this working correctly now is available here my-hugo-demo-site