1st of all, nothing was changed at the user interface / background processing of user requests at “Admin menu access” add-on with 4.29 update. As earlier plugin sends standard jQuery AJAX request to the web server and gets back the HTML data to fill the form shown at the modal dialog window.
Is there any chance to get more detailed information what thing in the AJAX request is not liked by your antivirus. May be some information from the antivirus logs?
Does antivirus block other add-on buttons like “Posts Edit”, “Posts View”, “Meta Boxes” too?