Problem with Brave browser

I have a problem with getting Contact Form 7 to work with Brave browser. When I click the submit button, there is no response.

Looking inside the console, I get the following messages:

Failed to load resource: the server responded with a status of 404 (Not Found)

and

POST http://playability.de/wp-json/contact-form-7/v1contact-form-7/v1/contact-forms/238/feedback 404 (Not Found)

(This path looks like nonsense to me, not sure how it’s generated)

Can anybody help me with this? the plugin works fine in Safari, Firefox and Chrome

The page I need help with: [log in to see the link]