I see the problem.

If you try to open other author post (like 103) at the back-end post editor via direct link:
you will get permissions error message:
Désolé, vous n’avez pas l’autorisation de modifier les entrées dans ce type de contenu.

It’s possible if front-end editor code does not respect permissions set by WordPress. For example it may check if current user can edit_posts, but it may does not check if current user can edit this post ID=103 and send update directly to the database.

Could you send me (support [at-sign] role-editor.com) this front-end editor code (plugin or theme) copy for the investigation?