Appian Academy blank pages bug

I'm encounetring a problem with Appian Academy, where after completing a part of the course (when green checkmark appears)
trying to see the content results in a bug, where the content is displayed for a couple of seconds, and then goes blank, as in the screenshot below.

If I go to Course evaluation, and then back to course content, I can see the content for about 3 seconds, and then it dissappears again.
It only happens with courses, or parts of courses that I completed (green checkmark).

Has anyone experienced this bug? Do you know how to fix it?