Autocomplete not running on the third field

I've got a couple of fields with autocomplete running on them and populating hidden fields - but on the third field, which is just a cut and paste of the second it doesn't even fire. For the first two I can "inspect" and look at the network tab and see my keystrokes being translated into ajax requests. The third - nothing happens, nothing in network, nothing in console.

Any ideas?

<script type='text/javascript'> $(function() {
        $("#RegistrationTradingname").autocomplete({
            source: "/registrations/getTradingName",
            minLength: 2,
            select: function( event, ui ) {
                if (ui.item){
                    $('#RegistrationMembershipId').val(ui.item.id);

                    console.log(ui.item.value);
                    console.log(ui.item.id);
                }
         
            }
        });

        $("#RegistrationName1").autocomplete({
            minLength: 2,
            cacheLength: 0,
            source: function( request, response ) {
                $.ajax({
                    url: "/registrations/getMemberName/",
                    dataType: "json",
                    data: {
                        membership_id: $('#RegistrationMembershipId').val(),
                        term: request.term
                    },
                    success: function(data) {
                        response(data);
                    }
                });
            },
            select: function( event, ui ) {
                if (ui.item){
                    var res = ui.item.value.split("|");
                    $('#RegistrationFirstname').val(res[0]);
                    $('#RegistrationName').val(res[1]);
                    ui.item.value = res[0]+' '+res[1];
                }
            }
        });

        $("#RegistrationName2").autocomplete({
            minLength: 2,
            cacheLength: 0,
            source: function( request, response ) {
                $.ajax({
                    url: "/registrations/getMemberName/",
                    dataType: "json",
                    data: {
                        membership_id: $('#RegistrationMembershipId').val(),
                        term: request.term
                    },
                    success: function(data) {
                        response(data);
                    }
                });
            },
            select: function( event, ui ) {
                if (ui.item){
                    var res = ui.item.value.split("|");
                    $('#RegistrationFirstname2').val(res[0]);
                    $('#RegistrationName2').val(res[1]);
                    ui.item.value = res[0]+' '+res[1];
                }
            }
        });

    });
</script>

HTML:

 

Oh, I know that one well, I don't think so...

 

Ryan - you were right on the money and I didn't see it staring me in the face! Realised that my hidden field and my display name had the same id, didn't happen to the first because the display name had a 1 while the hidden fields didn't.