Dear Lucie,
It looks like you have a bespoke setup that adds the
CSS class 'role-none' to the 'body' tag and that hides section zero / course format content in the main region, that contains the two modules on the course with in section 0, being id 228 in the URL of the course index. The rest of the content is within custom block regions generated by the theme. As the course index only knows about the
sections and content in the course format generated output, then that is what it shows. There has been a change to this for with URL's moving to section id's instead of section numbers, I had thought this happened in M4.5, but seen that it happened in M4.4 too. As I don't know what you upgraded from then I cannot determine the nature of how your solution could have worked before with section 0 in the course index having the course URL with its id instead.
In any event, the solution would possibly be having a custom course format that altered the 'get_view_url' method in the course format lib.php or you changed the core one.
G
