cart_id was not returned in addToCart AJAX call

-- HikaShop version -- : 4.7.0
-- Joomla version -- : 4.2.6
-- PHP version -- : 7.4.30
-- Browser(s) name and version -- : Firefox 108
-- Error-message(debug-mod must be tuned on) -- : cart_id was not returned in addToCart AJAX call hikashop.js:1151:13

Hello,

Recently my client discovered a problem with Hikashop order process.
On adding a product to cart nothing happens and there is a JS error in the console:
cart_id was not returned in addToCart AJAX call hikashop.js:1151:13
On second try (second Add to Cart click) it goes fine, but we have a choice: "continue shopping" or "go to checkout". Whatever we do, in few seconds we are redirected to checkout.

Problem happens in Firefox mostly.
There are more errors of this type.

Please help.

Thanks

1) The add to cart problem was - I think - caused by this plugin
www.joomlashack.com/joomla-extensions/ospam-a-not/
I disabled it now and it's fine.

2) I changed the settings of the notification plugin and it's ok as well.