Product Variant Dropdown not working correctly

[rkasper]

Hi,

I am currently having a problem with my shop. After updating from version 1.6 to version 1.7.8.9 the dropdown fields for article variants are not working correctly anymore. If I change the selected variant it automatically jumps back to the preselected one. I cannot see any issues with debug mode enabled or in the console of Chrome.

Do you have any idea how to fix it?

[prestahero.com]

Hello,

Are you using the default theme or one customized for your site? Usually, this error occurs because the theme has an error in the "core.js" file.
You can try to fix it by copying the "core.js" file in PrestaShop's default theme to the theme you're using.

Best regards.