Hello,
I've noticed that some xajaxResponse methods has been modified in ONA files (like /opt/ona/www/include/xajax/xajax_core/xajaxResponse.inc.php for example). These functions are needed in the rack_maint.inc.php file.
As I can see, the xajaxResponse::addAssign() method would have been replaced by the xajaxResponse::assign() method, and it might be the same case for the xajaxResponse::getXML() method.
I didn't make further researches, but I suppose this plugin needs to be updated.
I hope this will be useful for you
Thank you in advance !