How to stop tinyMCE 5 to add ../../../../ before an absolute url received from alexusmai filemanager?

I am using Laravel 8, tinyMCE 5 and Alexusmai filemanager. My images are in the /public/assets/images folder. The 'assets' disk is setup in config/filesystems.php :

    // assets folder in public path
    'assets' => [
        'driver' => 'local',
        'root' => public_path('assets'),
        'url' => '/public/assets',
        'visibility' => 'public',
    ]

FM returns the correct relatrive url, i.e. public/assets/images/xxx.jpg in a form field as a stand alone.

In tinyMCE 5, the same url is returned to the editor (the image is visible) but as soon as I look in the source3 code, the img scr is replaced by "../../../../public/assets/images/xxx.jpg". Why? How can I stop tiny to do that?

via Chebli Mohamed