he confirm exit solution does not work correctly for multiple forms on one page because the serialized data are generated over an collection and not over the single forms.

Resources/public/base.js

@@ -1,7 +1,7 @@
 jQuery(document).ready(function() {
     jQuery('html').removeClass('no-js');
     if (window.SONATA_CONFIG && window.SONATA_CONFIG.CONFIRM_EXIT) {
-        jQuery('.sonata-ba-form form').confirmExit();
+        jQuery('.sonata-ba-form form').each(function () { $(this).confirmExit(); });
     }
 
     Admin.setup_select2(document);