We noticed that for some messages we receive the WhatsApp Status Webhook (Sent, Delivered, Read) but for some others we receive only (Sent, Read) . Do you know why this happens?
This is an expected behaviour of WhatsApp, for a status to be read, it must have been delivered. In some scenarios, such as when a user is in the chat screen and a message arrives, the message is delivered and read almost simultaneously. In this or other similar scenarios, the delivered notification will not be sent back, as it is implied that a message has been delivered if it has been read. The reason for this behavior is internal optimization.