I have registered a Webhook in order to handle shipments when an order is created.
My app was working fine while testing it with an order sample (from here Webhooks) but then when I set up a development store, the shipping_lines parameter is empty (I get an empty array), the rest of the request body seems ok, but this parameter is missing. I don't know what can be happening.
Besides, my app is programmed to always respond with a 200 OK code even if there's an error. But Shopify keeps sending the same request several times. In the docs it is said that a 200 OK is considered successful (Responding to a Webhook), so Shopify is supposed to make the request once. I don't know either why this happens.