As you have seen, I have made some changes by restoring the sidebar functionalities and modifying the theme. I debugged quite a lot of things without encountering any particular problems, but if anyone should encounter any forum error, please let me know so that I can fix the problem. Thank you...
Actually the bug was there before. In the sense that some content should only be visible if logged in, especially since the function shows recent content. So actually now it works as it should, not before...