I have a problem to which I just can't find a solution to, unfortunately.

We run a Shopware 6 v6.4.1.0 online shop.

Whenever someone tries to register, the registration doesn't go through because the "continue" button at the end shows the following error:

After some digging, I noticed that the checkbox for "different shipping address" doesn't work properly. On a freshly installed SW6 shop it display's an additional address form when the box is checked. This works by changing CSS classes via JS (it basically just toggles from display:none to display:block).

I have already tried deactivating/uninstalling Plugins and switching Themes but nothing fixed this.

I really don't know what to do anymore.

Help would be appreciated.