I then started removing chunks from my HTML page one by one and stumbled upon a tag removing which fixed the duplicate request problem. And this tag was, to my surprise, a little innocent tag.
It turned out that tag had “#” as its src. As soon as the page (let’s say “localhost:3000/edit-content?id=xxx”) loaded, browser sent another request to “#” to pull content of the image. The “#” translated into the URL of the same page (i.e. “localhost:3000/edit-content?id=xxx#”), hence my controller at server received duplicate requests for one page.
So I reset the initial “src” of the tag to an empty string which finally fixed the problem.