Stacking modals scrolls the main page when one is closed [duplicate]

Answer 1

Backdrop's not the problem. Not being able to scroll through shown modals if the top one is closed is.

You should add the following Javascript:

$('.modal').on('hidden.bs.modal', function (e) {
    if($('.modal').hasClass('in')) {
    $('body').addClass('modal-open');
    }    
});

demo: http://jsfiddle.net/u038t9L0/1/

When the body has class modal-open the following CSS will be applied for your .modals:

.modal-open .modal {
  overflow-x: hidden;
  overflow-y: auto;
}

Closing the modal will remove the modal-open class from the modal too.