Note: Below is the original page from the Bootlint documentation, some of the info here might not apply to Bootlint-NG!

A .panel-body must be a direct child of its .panel or .panel-collapse. No levels of intervening elements are permitted between the .panel-body and the .panel or .panel-collapse.

Wrong:

<div class="panel panel-default">
  <div class="my-super-special-wrapper">
    <div class="panel-body">
      Basic panel example
    </div>
  </div>
</div>

Right:

<div class="panel panel-default">
  <div class="panel-body">
    Basic panel example
  </div>
</div>