how the "complete order" button works

-- HikaShop version -- : Business: 2.6.4
-- Joomla version -- : 3.6.0

the situation is the following: the cart is ok,everything works. The order accepted. But the "complete/finish order" button doesn't work from the first click, only if you click twice. Irrespective of type of browser or device. The page refresh and stay in the same state. no errors. At the same time I can see in the page code that it is one and the same button. And in logs it is the same thing.
But as a result the order is accepted only once.

solved