Failed to execute ‘postMessage’ on ‘DOMWindow’ (...) error on inital load

[gammaw]

Error (see in console): Failed to execute ‘postMessage’ on ‘DOMWindow’: The target origin provided (‘https://www.mixcloud.com’) does not match the recipient window’s origin (‘https://www.mmmnmnm.com’).

Blog posts (debugging hints):

• Failed to execute 'postMessage' on 'DOMWindow': The target origin (https://....) provided does not match the recipient window's origin ('https://...') davidjbradshaw/iframe-resizer#443
• Failed to execute 'postMessage' on 'DOMWindow' when another iframe is present soundcloud/soundcloud-javascript#15 (comment)

Other hints:

• Mixcloud API implementation bug (baxgas)?
• Error doesn't occur in Microsoft Edge (Windows 10)