AngularJS drag and drop twitches

Question

I learn AngularJS Drag and Drop. My code is working correctly. I move between each other DIV.

app.directive('draggable', function() 
app.directive('droppable', function()

But when the DIV contains elements that animation is choppy. You can try it myself as an example:

Sample plnkr

How can I get around this problem? Thx.

Upd. Works poorly only in chrome. In firefox everything is acceptable

Upd2. I found it Issue: Bug

Answer 1

I found here answer

  .child-elements {
  pointer-events: none;
}