Hi,
If you have two cart modules on the page and the "Use AJAX when possible for add to cart buttons" setting activated, then only the first one will refreshif the AJAX system is used.
Next version of HikaShop will have a new cart system which will be able to handle several cart modules refresh in ajax and an ajax system which can work in any case. But for now, there is no easy solution.
With the option turned off, both cart modules should always refresh.
Regarding the default values, it's the other way around. With the ajax option turned on, the add to cart is done without a page refresh and thus you keep the selected options after the add to cart. But with the ajax option turned off, the whole page is refreshed and thus you get back the default options after the add to cart. There is no easy solution either with the current version of HikaShop I'm afraid.