Hi,
I have fixed, there was a issue with the plugin called "System - Regular Labs Library". This plugin uses function of Joomla HtmlDocument class, but all ajax requests (like notifications or profile preferences) are Raw content (so raw and not html).
Since Easy Profile define the document type from our "Easy Profile - System plugin" then it need to be loaded before the plugin "System - Regular Labs Library".
The fix was simply to move "Easy Profile - System plugin" before the "System - Regular Labs Library" plugin from Extensions->Plugins