You can try the solution from the original post:
themes/modules/ps_shoppingcart/modal.tpl removed:
data-dismiss="modal"
themes/modules/ps_shoppingcart/modal.tpl added:
1. custom-modal class to "Continue Shopping" button and "X" button
2. <script> $(document).click('.custom-modal-close', function() { $('#blockcart-modal').remove(); $('.modal-backdrop').remove(); $('body').removeClass('modal-open'); }); </script>
Let me know if you manage to get it work. Remember to clear cache after applying these changes