I ran into this issue due to a programming error that caused an infinite loop in my JavaScript code.
Some time ago Chrome would point out that a script is stuck, but for some reason such a message did not show up in my Chrome. Instead, I found this error in the network tab.
Trying Firefox, it showed the error message "This page is slowing down Firefox. To speed up your browser, stop this page".
This helped me figure out that in my case the issue was not related to the request, but was actually caused by a script running forever.
Apparently, the infinite loop in JavaScript causes Chrome to not finalize the request or at least it does not update this display. I am not sure why Chrome would not show a more meaningful error message that a script is stuck.