Adding a random item to an order, Opencart?

Question

opencart

Good afternoon!
The site on opencart version 2.1.1, noticed that when you add a product to the cart, 1 product is added, you place an order, it shows 1 product on the checkout page. And when you confirm the order, it shows in the mail and in the admin panel that 2 products have been issued, 1 product that you have chosen, and the second one is random. I can’t understand what’s wrong, the site does not show errors, it works fine, the error log is also empty, can someone tell me what could be the problem?