Courses always look empty while lessons are assigned

Good morning,

I created some courses and in each course sections and lessons. When I go to the frontend, everything is displaying properly. However in the backend, when I open a course, I see the sections with NO lessons inside. If I create a new section, it appears on the frontend but not on the backend. Same if I delete one, it still appears in the backend while the frontend is correctly updated.

There is thus no way for me to assign/unassign lessons to courses since the backend is not displaying properly.

I’ve checked all other topics related to this issue and could not find anything working here.

Regards,

Jonatan