>Is this error also in VFP9 Textboxes?

Of course.

On VFP9 SP1b1, if you edit the textbox
and Text='01-01-200',
then Value='01-01-0200'.

If you press TAB, only Keypress(9,0) is fired,
the TextBox doesn't write the value into the (ControlSource).

If you click over another form's control,
only a Form.MouseUp , Form.click are fired ( none MouseDown )

The TextBox.Error() it is ignored because this is a Property error.
You can capture it with ON ERROR only,
but only when you try to deactivate the form.

A little start point:

* interarctivechange
IF this.Value>={^1601-01-01} OR EMPTY(this.Value)
	ON ERROR
ELSE
	ON ERROR _SCREEN.ActiveForm.ACTIVECONTROL.Value = {}
ENDIF