Hello João,
Silk UI approach to responsive is a bit diferent.
When you are in a production environment, the device simulation is always off (unless you usethe site property).
So, if you are in a desktop, you will always see the desktop experience, no matter what the resolution is.
We do provide you with some classes that you can use to customize your own css to better adjust to the specific resolution of your screen.
Last but not least, you solved your issue by changing the javascript code inside the eSpace SilkUIFramework.
This is not recommended, because whenever you want to upgrade to the latest version of Silk, you will have to do it by hand, which can be quite difficult.
Please let us know if you have any other questions.
Cheers,
Samuel Jesus