Hi @florinschweiz, thanks for sharing more details with us!
When you check the Force shipping to the customer billing address, means that you don’t need your customers to enter a separate billing address, is that what you’re trying to do?
Also, I can see an issue coming from the Wallee plugin on your checkout page.
So, to help us diagnose it better, can you give a full conflict test a try, please?
The best way to determine this is to:
- Temporarily switch your theme to Storefront
- Disable all plugins except for WooCommerce
- Repeat the action that is causing the problem
If you’re not seeing the same problem after completing the conflict test, then you know the problem was with the plugins and/or theme you deactivated. To figure out which plugin is causing the problem, reactivate your other plugins one by one, testing after each until you find the one causing conflict.
Since your site is live, I’d recommend doing the test above in a Staging site.
If your host doesn’t offer that option, we recommend WP Staging for quickly spinning up a new test site.
Let us know how it goes! My very best,