I already commented on https://github.com/gohugoio/hugo/issues/4539 and I followed the advice to post it over here.
Look here for a simple test site: https://gist.github.com/ManuelHu/1d9bda66b8dfa62f3ee8fab7611ca6f5/raw/c47260e8a4caf101362aee314bd18fdb4b22827a/test.zip This is obviously not my real site, but it shows the same problems as my site and uses the same theme.
How to reproduce my problem: Run hugo server (>=0.32) and visit it in a browser. The home page works just fine, the page labled X shows a 404. At least this is the case for me.
In server mode, I can fix the issue by renaming the file x/index.md to x/index1.md and back. After a reload in the browser the page shows up. Of course, the problem can’t be fixed like that in “normal” static output mode.
In hugo version 0.30 and 0.31 everything works fine. Maybe it’s dependant on the theme (hugo-material-docs), but there are no error messages shown in the console.
Hugo version: 0.37.1
OS: Windows 10
I would be glad if someone could help me!