Item not added to bitrix cart?

Question

1C-Bitrix

Good afternoon, when viewing a product in the catalog, if you use the quick addition, then the product is either simply not added, or 2 pieces go to the basket at once.

At the same time, if you go to the product card, then there are no problems, everything is added correctly and in the right quantity.
On the default template everything is ok.
What could be the reason?

Answer 1

The reason may be in incorrect JS code or PHP. Can't tell from the screenshot. Dig all the way from clicking the add to cart button.