Cart problem in Virtuemart 1.9 site

Product has as added required option before you can put it in cart. But this function is not working the right way. Some products get the option in the screen and when they fill in it goes to cart without the page of the cart showing. Some products can go to cart wihout the required option warning showing up but then the page of the cart is showing up . Both are not right. What has to happen. If a client do not fill in the option he gets the warning before the product can put to cart and if he did well, then shows up the page of the cart and he can choose to shop further of want to check out.