title: WPF TabItem doesn't lose focus
body: <p>I have a tabcontrol binded the an observable list. Eveything look to be perfect until I select a tab. Once selected, the tab doesn't lose its focus and the selected tab is not available. They are not any message in the Output Window.</p>
  
  <p>Here is a screen shot just before clicking the tab:</p>
  
  <p><img src="https://i.stack.imgur.com/bIruY.png" alt="alt text"></p>
  
  <p>And here is a screen shot after (with the problem):</p>
  
  <p><img src="https://i.stack.imgur.com/mkrgA.png" alt="alt text"></p>
  
  <p>Any idea about how to resolve this problem or any hint to be able to debug this kind of behavior?</p>