php - SendGrid webhook not receiving events

I created webhook for tracking Sendgrid email open,click events. I received event data in webhook like this:

$data = file_get_contents('php://input');
$data = json_decode($data);
Copy code

It's worked fine when I send a mail to single receipt. All processing, delivered, open, click events to my webhook.

If I send mail to multiple receipts (5 to address) only few events received to my webhook. But in Sendgrid dashboard activity log having all events. Why am I not able to receive these in my webhook?