It was missing the variable %object% in message_delete_confirmation translation from SonataAdminBundle:CRUD:delete.html.twig
@@ -184,7 +184,7 @@
</trans-unit>
<trans-unit id="message_delete_confirmation">
<source>message_delete_confirmation</source>
- <target>Are you sure you want to delete the selected element?</target>
+ <target>Are you sure you want to delete the selected "%object%" element?</target>
<trans-unit id="btn_delete">
<source>btn_delete</source>