Flex :: Tab Order - Explicitely Setting TabIndex Does Not Work?

I've got a problem with following example code in flex:

Test.mxml:

<?xml version="1.0" encoding="utf-8"?>
<s:WindowedApplication xmlns:fx="http://ns.adobe.com/mxml/2009" [code]..........

When I start the application and press Tab to cycle through controls, the focus jumps to the first text box, then to the first radio button of the first TestComponent, and then directly to the last textbox missing the second and the third TestComponents.

UPD: Explicitely setting tabIndex does not work either:

<?xml version="1.0" encoding="utf-8"?>
<s:WindowedApplication xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"[code]...............