Curriculum page becomes unavailable every few minutes

UPDATE: a free vpn extension solved this.

Every few minutes the curriculum page ( becomes unavailable, while everything else is working. It can be accessed neither via “curriculum” button in the nav bar nor the large “Go to the coding curriculum” one at the bottom.
The error message i get is this:
The breakdown lasts for up to 30 minutes and seems to be happening randomly, but there is a pattern I have noticed:

  • Right before this happens, the word completion stops working and check marks stop appearing next to completed tasks. I’m still able to move through tasks and submit answers, but when I go to the curriculum page I see that at least some of the recently submitted answers are not marked as completed. If i reload the page, it becomes unavailable. If I don’t reload the page and continue advancing through tasks even though check marks are not appearing, after submitting a couple of answers I get stuck with the task I’ve already submitted. The address bar is changed and I know that I’m supposed to be at the next task, but I’m stuck with the previous one, although it is not frozen, i can scroll, edit, press buttons. If i submit it again, nothing changes, If i reload or try to go to the curriculum page the page goes down.
  • When I complete my first task after the page has become available once again, I always get the pop-up asking for monthly donation. I don’t know if this is relevant, but still decided to include.

The issue is present with Firefox, Chrome, Opera. I’m located in Moscow, Russia, not using adblock or vpn.