Hi,
We do our best to keep backward compatibility with the views and we test hikashop as much as possible before the release, but there is so much options and possible conflicts with other extensions or joomla updates that we find bugs even on the vanilla release so it's normal that if you modify your views and don't port your modifications to the new version of the views you get problems from time to time. As much as possible, you should try to use CSS to modify the look of the views. That way, that won't create such bugs.
Also, if your website is already on production, you shouldn't update HikaShop until we activate the update. We released the new version yesterday so there might still be problems with it. That's why we lock the update and that you have to download it on our website if you still want to update from the previous version to the latest version:
(The update is not yet downloadable via the update menu of HikaShop as we are waiting for feedbacks before rolling it out. If you want to update, you can download it directly on our website. It is available on the download page for the Starter edition and on your order details page for commercial editions)
PS: Looking at the video I found another problem: The quantity system was not working properly in some cases and you were getting several lines on the cart for the same product where you should have had only one line with the quantity increased. I've run some tests and was able to reproduce it on our end. We fixed it, did some tests and uploaded a new build of the current version which fixes the problem. So you can download again the package from our website and install it again in order to get the fix.