Error Messages
From Documentation
This section explains those common error messages you might encounter during developing with ZK, so that you can figure what's going wrong and eliminate them.
The Server is temporarily out of service
The is the default browser-side error message which is displayed after sending an AJAX request.
Runtime Exception
out of sequence
https://potix.freshdesk.com/helpdesk/tickets/5785
contentId is required
The resource you request is no longer available
The resource you request is no longer available: /ui/handling.zul (z_na20). This is normally caused by timeout, or opening too many Web pages. You have to reload the page and try again.
client error
Severe: [Desktop z_wew:/mypage.zul] client error: Failed to mount: Cannot read property 'colSpan' of undefined