aalisg Hi
I tested that page with Cassiopeia - a default Joomla template but the same issue happens, which means that the issue must be from the integration of RSJoomla! extensions.
You can try this testing and forward to that developer:
1- Go to Backend >> open menu item of this page: https://www.li-alumni-dev.org/fr/oib-2023.html and assign it to Cassiopeia template:
2- On frontend, it looks the same as our template:
