steps to reproduce

1. run the code below with the attached viewmodel

   <zk>
   	<div apply="org.zkoss.bind.BindComposer"
   		viewModel="@id('vm') @init('support.issue.ZK3578VM')">
   		<button label="toggle" onClick="@command('toggle')"></button>
   		<grid vflex="1" visible="@load(!vm.showColumn)">
   			<columns>
   				<forEach items="@load(vm.columnList)">
   					<column label="@load(each)" width="150px" />
   				</forEach>
   			</columns>
   		</grid>
   	</div>
   </zk>
   

2. click the button 2 times

current result

the column disappear.

expected result

the column is still visible.

debug info

• The actions below will make the bug be non-reproducible
  • remove vflex="1" on the grid
  • don't notify change on the ListModelList. But users might use java collection object
• it only happens in Safari 8, 10, not on Chrome, firefox

workaround

• don't notify change on the ListModelList.