Questions?

Hello, I have got an issue in webhook authentication.
I enabled basic authentication for my webhooks and filled in user and password.
When I send the test payload from the webhook setup page the authorization header content is correct and everything works fine.
When actual survey data is coming to the webhook though, the authorization header is not what I expect. When I decode the base64 value I get two strings made of hexadecimal digits that are unrelated to my credentials.
Can you help?
Thanks,
Regards