Iframe not showing. error message "frame-ancestors 'self'

Hi

I need to embed an Iframe on an other site of our Webflow site (Paid Webflow Hosting and custom Domain) but somehow the Iframe does not load and the following message shows up in the console.

Refused to display ‘https://www.parley.ch/watchlinks-editor-embed’ in a frame because an ancestor violates the following Content Security Policy directive: “frame-ancestors ‘self’”.

How I understood from an other older topic, this should only show on the *.webflow.io site and not on the custom domain?

Here is my share link

So, i learned that at the Ecommerce service the “Secure frame headers” can’t be deactivated.
Is it possible to whitelist some certain domains so they could show the Embed Iframe?
The page we have to display is without Ecommerce function. There is no Cart or Product on that page.

I hope somebody could help and possibly let me know about the options.