Embed widget - working in preview, but not on player

Embed widget - working in preview, but not on player

I'm trying to use the Embed widget to show a playlist from an internet radio station.
The code is generated by this website:

When using the preview feature for a playlist or layout where the Embed widget with the internet radio station playlist is present, the content loads perfectly and everything looks good.

However, when the player shows the Embed widget, the content doesn't load.
Only the headline is present. No playlist information and no graphics being displayed.

Is this a bug, or are there some limitations to the Embed widget that I need to compensate for?