Combobox losing input characters

Steps to Reproduce

http://zkfiddle.org/sample/27n8vht/4-Combobox-losing-input-characters

Start typing characters to trigger the combo-popup and drill down possible choices.

e.g.: a, f, t, [backspace], [backspace], f, t, [backspace], [backspace], ... repeat

Current Result

Using varying typing speed sometimes typed characters are removed from the input element. 

Expected Result

characters once typed should remain in the combobox and be used to drill down the choices 

Debug Information

Seems to relate to the onChanging interval of 350ms

Workaround

commented out in the linked zkfiddle example

    zk.afterLoad('zul.inp', function() {
      var xCombobox = {};
      zk.override(zul.inp.Combobox.prototype, xCombobox, {
        setRepos : function() {
          this.valueEnter_ = this.getInputNode().value;
          return xCombobox.setRepos.apply(this, arguments);
        }
      });//zk.override
    });//zk.afterLoad