- open the attached document
- focus the top-most control
- repeatedly press tab, which travels through all 5 controls in the document
- note that the traveling does *not* happen top-to-bottom, instead, first the
  text fields are traveled, then the check box, then the button
- switch on the design mode
- in the property browser, look at the "Tab Order" property of all 5 controls.
Note that
  the values are "1" to "5", from top to bottom
=> the "Tab Order" values suggest that the controls should be traveled
top-to-bottom,
   however, they obviously aren't

Renaming two of the 3 text fields from "TextBox" to something else, so that all
controls have different names, solves the problem.