Error after adding the "Discussion" element

Hello, I have a problem with adding the Discussion element to the training. Maybe someone on this forum have encountered similar issue. When I’m adding the Discussion below a video in a new unit and click “View Live Version”, the following error pops up: This discussion could not be loaded. Refresh the page and try again.. I’m not sure what is causing this error. Any help would be appreciated.

Here are some screenshots:
Adding the element: 1 hosted at ImgBB — ImgBB
Error: 2 hosted at ImgBB — ImgBB

Staff debug info:

Has no one encountered this issue before? Any help would be appreciated.
I’ve noticed that the error is visible when adding the Discussion below the video.
If the Discussion is added without the video element, there is no error.