Hello,
We had just process some tests on your website and so far didn't see anything weird in your Guest Checkout.
So, in order to better understand what's going on, can you be more specific by providing these elements like :
- A step by step process in order to be sure to reproduce your issue
- Your Checkout configuration screenshot, and more especially your Login & Registration part
- Any elements that can help us to better understand the issue, like what did you expect and the result, screenshot with annotation, etc etc
Awaiting news from you to be able to help you.
Regards