Why, when sending a message to the Vkontakte group, the callback api sends the ego periodically again instead of one request?

Question

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When a message is sent, a request is sent to the server. Then comes the answer. But since instead of one request, VK sends the ego again for reasons I do not understand. And the answer comes every time and spam is obtained. Also return unsuccessful requests come with an error: "incorrect response text" but the answer comes. Can you help me figure out why requests/responses are being spammed?
error screen.

Answer 1

Your server must respond with two "ok" characters with status 200. Otherwise, VK will send the request again.

Please note that after receiving a notification, your server should return the string "ok" and HTTP status 200. If the server returns an error several times in a row, the Callback API will temporarily stop sending notifications to it.