After reading the jquery-doc the answer is fairly easy:

Change:

$('#btnModelConfirmMessage').on('click',function () {
        fun();
        $('#msgModal').modal('hide');
});

Then add a new call on the hide.bs.modal event

$('#msgModal').on('hide.bs.modal',function () {
        $('#btnModelConfirmMessage').off();
});

This removes the previously added handler, so we do not stack-up the events.

Hope someone will find this usefull :))

Cheers, Daniel

Trigger click event on a[href$="#Modal"].

Copy$('a[href$="#Modal"]').on( "click", function() {
   $('#Modal').modal('show');
});

Copy<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"></script>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" rel="stylesheet"/>

<!-- Trigger the modal with a button -->
<a href="#Modal" class="btn btn-info btn-lg">Open modal</a>
<!-- Modal -->
<div id="Modal" class="modal fade" role="dialog">
  <div class="modal-dialog">

<!-- Modal content-->
<div class="modal-content">
  <div class="modal-header">
    <button type="button" class="close" data-dismiss="modal">&times;</button>
    <h4 class="modal-title">Modal Header</h4>
  </div>
  <div class="modal-body">
    <p>Some text in the modal.</p>
  </div>
  <div class="modal-footer">
    <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
  </div>
</div>

  </div>
</div>

EIDT: changed myModal to Modal