How to solve the problem with the VK API messages.send method?

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Good afternoon.
The problem is this: I send messages to my friends with a delay of 800ms using the messages.send method. After about 20 messages, the method starts returning an error with code 7.
Error description: "You do not have permission to perform this action. ". Checked, there are rights. Through the VK website, you can send a message to people on whose id an error is returned.
The problem appeared a couple of days ago. Before that everything worked.
I tried to change the token.
I also tried changing the app.
Tell me how to overcome the error?