Lab's PDF files not loading followed by 408 error

Hi everyone!

I'm wondering if someone else is facing the same issue as I do.

When I'm doing the course using my notebook running Ubuntu 20.04, I got an error when accessing the Lab sections of the chapter.

Generally, the Labs from the couple chapters I do for the day works good but then on the next the issue happens.

Browser tries to load the PDF content but after a while, a pop-up with an error is displayed:

If I reload the page, as the pop-up suggests I get a 408 (timeout) error:

Therefore, I cannot access any course content or navigate to any Linux Foundation's page unless I clear the browser cache.

This is really frustrating since I have to do it frequently and recent course progress is lost !!

I tried to use Chrome and Firefox, be sure they are updated as the system packages as well but the issue happen on both browsers.

I noticed the same issue doesn't happen if doing the course from a Windows machine : (

If someone else faced the same and has a solution for this problem, I'll really appreciate you sharing.

Thanks!