IE 11 issue form getting submitted twice

Hi Experts, I am working on a website written in  classic asp and .net.
There is a particular code snippet which needed a change.The flow is from a modaldialog popup which is an .asp page to another intermediate(without UI) .asp page for this change.No, aspx involved. AFter the change, on debugging via F12 developer tools, I see that for some reason, on IE button click, the code snippet fires twice while on firefox all is good.There is a single post seen for firefox.Below is my code snippet :Please Help.

if (window.opener== null)      {      
                                          
                                    window.dialogArguments.form1.action = "/includes/test.asp?page=somedotnetpage&id="+window.dialogArguments.form1.HidclientID.value;
                                    
                                    window.dialogArguments.form1.PIN.value = document.form1.pin.value;
                                    window.dialogArguments.form1.submit();
                        }
                        else {                                          
                                  window.opener.document.getElementById("form1").action = "/includes/test.asp?page=somedotnetpage&id="+opener.document.getElementById("HidclientID").value;
                                window.opener.document.getElementById("PIN").value = document.getElementById('pin').value;
                                                                              
                                    window.opener.document.getElementById("form1").submit();                                    
                        }