title: spring mongodb not saving newly added field
body: <p>this is my mongo db document</p>
  <pre><code>classA {
  private String name;
  private long elapsedTime; // newly added field
  }
  
  @Document
  classB extends classA{
  private String id;
  private String owner;
  }
  
  classBRepository.save(classBObject);
  
  </code></pre>
  <p>but newly added elapsedTime field is not saved to database, others are saved. if I call save method second time then that field is saved.</p>
  <p>I am not using any strict schema configuration by the way.</p>
  <p>What do you think that can cause this problem ? is it because of some configuration, is there anything I am missing here ?</p>
  <p>MongoDb version: 5.0.6</p>
  <p>Spring version: 2.6.6</p>