Example site here. Run it in hugo server mode. Then, open /test/ page. Now, edit content/test/doc.md file. Notice in the terminal that hugo notices change, runs rebuild, but still render the old content.

It seems to be related to markdown files only, as other files do reload fine.

What version of Hugo are you using (hugo version)?

$ hugo version
hugo v0.123.0-DEV+extended linux/amd64 BuildDate=unknown

Does this issue reproduce with the latest release?

No, hugo 0.122 and before it works fine.