title: Is it possible for UserDefaults.standard.removeObject(forKey: ) to fail?
body: <p>I was trying to reproduce a strange bug in one app I'm working on, and it seems the only possible reason for the bug to happen would be that <code>UserDefaults</code> sometimes fails to remove the object.</p>
  
  <pre><code>UserDefaults.standard.removeObject(forKey: Constant.name1)
  UserDefaults.standard.removeObject(forKey: Constant.name2)
  </code></pre>
  
  <p>When I test using the code above, it is working fine on my end, but it seems that there is some case (iOS version? Memory conditions? Other?) where this code fails for some of our users, and the app keeps those UserDefaults forever.</p>
  
  <p>Is that even possible? </p>
  
  <p>I found some radars on OpenRadar that points towards the fact that <code>UserDefaults</code> are not saving correctly, but no confirmation that it really happens.</p>