Multiple User Notifications (autoresponders)

I have a form for an event registration where one person and register up to 6 attendees.
This was working when I initially set it up with merge tags in the BCC field. It seems to have stopped functioning now. The BCC field works fine if you have comma separated email addresses in there, but the merge tags stopped working.

I tried using this hook, but had no luck. It actually broke all the other forms on the site.
The other forms would send the user to the websiteURL.com/form_page/:/

//email BCC to all registrants for Conference
add_filter("gform_pre_submission_filter", "add_bcc");
function add_bcc($form){
	//change 2 to your actual form id
    if($form["id"] != 28)
        return;

    //creating list of emails based on fields on the form
    $bcc  = $_POST["input_16"] . ",";
    $bcc .= $_POST["input_25"] . ",";
    $bcc .= $_POST["input_32"] . ",";
    $bcc .= $_POST["input_39"] . ",";
    $bcc .= $_POST["input_46"]; 

    //setting notification BCC field to the list of fields
    $form["autoResponder"]["bcc"] = $bcc;

    //returning modified form object
    return $form;
}

It just submitted without issue. No errors. But it didn't send the autoresponder to the merge tags in the bcc.