After upgrade ZK from 7.0.2 to 7.0.3 or 7.0.4, ZK page in a Liferay portlet becomes always hanging at "processing" prompt. Removing and readding portlet in Liferay page fixed the problem but only on the first run/load thereof, subsequent (second, third ...) runs/loads always hangs dead at "processing" prompt UI within 1s of the request. The zul file can just be as simple as a page with a ZK window with a ZK label. There are no server log messages. Zscript runs normally. The problem seems to be UI rendering abruptly stopped.
<?page title="new page title" contentType="text/html;charset=UTF-8"?>
<window title="new page title" border="normal">