Very slow loading after completing a course with question elements

Hello.

The problem is the following:

First the site is working fine. Then I make a course with few units with few text elements and few single and multiple answer elements, I enroll, I start learning. At this point the site is still working fine. BUT when I go in the units and answer the questions and finish some units, then all coursepress related pages of the site start working super slow! They can't even load. Other pages that are wp post and pages not related to coursepress are working fine.
Another interesing thing is, if I unpublish the course, now the problem is fixed. If I publish it again, the problem is back.

I have made a course now that has some answers answered and it is creating this problem and I have unpublished it so you can click around the site for example on the page /courses/ and see how it works great. Then go and publish it and try /courses/ and you will see the problem. (When the problem begins it takes some time for the slow effect to wear off, like a minute, even after unpublishing the course. I assume the server is recovering from the load or something. This is why it is easier to test first working fine and then with the problem, and not the other way around.)

The site is /nikolaytest1234 and the course is called: Slow test. I am granting support access now.

Thanks.