I am using WordPress 4.8, Woocommerce 3.1.1 [i.e. the very latest versions], and experiencing the problems described.
From the shop: https://shop.minecraft-skin-viewer.com, selecting the first product (t-shirt), the <div> section which contains the variations (size + color) is overlayed with transparent grey and the spinner continues forever. Impossible to choose either of the variants. The user is effectively blocked from proceeding further with a purchase.
This worked fine before upgrade to the latest versions of woo & wordpress