On this page, if you add an item to the Wish List, the dropdown selector disappears (at least in my Windows IE11 and Edge it does). If you don’t see it happen the first time, add a few more different-sized items to see it happen.
Okay, I’ve managed to find that there was 100% width applied to all <td> tags in that table. But now after a user adds an item, the selector box moves to the right instead of lining left with the label ‘Select Size’.