I have a similar question as "Leon Treff" --> 24 Jun 2018 19:11.
When I change the quantity of items in the Cart, then I click the "Update cart" button, there is no update.
My system cache plugin is disabled. I have a PHP version 7.2.12, with Joomla! 3.9.1 and Eshop 3.2.2.
I can add a product in the Cart, then when I am in the Cart I increment the number of items (for instance from 1 to 4), and I click the "Update Cart" button, but it does not react. If I refresh the page, I go back to "1" item.
I have tried with the navigators "Internet Explorer" and "Firefox", but it is the same result.
This is not related to Cache I think. It maybe a small isssue with translation. Please submit a new ticket to EShop category to send me the super admin account to the site so I can take a look at and resolve it for you.