Iframe audio player does not scale to the window size

In our activities, we use external URLs to embed an audio player from piksel, our streaming provider. For example, http://player.piksel.com/a/ibtr7f30

We use iframes as a solution. And until version 3.25., it works excellent. But since last updated, version 3.26, the player embedded on the iframe does not scale to the window size, and always keep the original size. 

Any solution for this, please?

PD: I attached images to help