Steps to Reproduce

<zk>
  <window border="normal" title="hello" height="600px" >
  	<div vflex="1" style="overflow: auto;">
		<textbox constraint="/.+@.+\.[a-z]+/: Please enter an e-mail address" />
    <div height="2000px" style="background-color: pink"/>
    </div>
  </window>
</zk>

1. focus in the textbox and move out to trigger an error box appearing
2. scroll down to make the textbox out of visible view port
3. click the pink area

Current Result

the error box disappears

Expected Result

the error box is still visible

Debug Information

• since 7.0.0, 8.0.0, 8.5.2.1, and 9.0.0.1, do the same steps, the error box is still visible
• since 9.0.1.2 including 9.1.0, 9.5.0.1, the error box will disappear.