1c-bitrix product price returns to the base price, excluding D7 modification?

Question

1C-Bitrix

Hello!
The version of the modules is the latest to date.
sale (17.8.5)
There is a product, it has a base price.
There is an infoblock with trade agreements that are linked to the counterparty ID and the discount is indicated. There is a formula that recalculates the price according to the discount and overwrites ['PRICE'].
Let's say the price of the product is 1000 rubles.
Counterparty discount 10%.
The product is displayed everywhere at a price of 900 rubles.
When transferring the goods to the basket, the price is saved 900r.
But when I take the basket and move it to the order:
$order->setBasket($basket);
The price becomes 1000r.
At the same time, if you print $basket before moving to the order, then the price is 900 rubles.
And right after the same $basket sets the price of the product to 1000 rubles. and becomes protected.
Well, when placing an order, 1000r falls, and not the expected 900r