I have debugged all day why this is happening to no avail. Luckily, I came across this minimal example that reproduces the issue perfectly. Just follow these steps:
Clone the project.
In en or de folder, rename post-2.md to post-1-top-ten.md.
Run hugo server.
Open post titled Post 2 in browser (now named post-1-top-ten.md)
Result: Post 2 inherits the post-1’s layout even though they are not related.
Expectations: Post 2 should inherit the default single layout.
git clone --single-branch -b hugo-forum-topic-40858 https://github.com/jmooring/hugo-testing hugo-forum-topic-40858
cd hugo-forum-topic-40858
hugo server
Well…thanks for figuring that out. I was creating a series of items that will share a few words and then different last parts. For proper organizing, I would prefer to maintain my designated order, but for now, I will find a way to do it differently until this is solved.