Images doesn't scale - Center fill mode
- The images doesn't respond when the browser width changes.
The issue happens because of the center background fill mode which works that way that it simply puts the image behind the slide and it keeps the image's set Focus point (by default, it's the middle of the image) in the slide in every responsive scenario. This mode does not resize the image, so if the slider gets smaller, the image won't. Instead, the image will be cropped.
You should change the image fill mode to fill or fit instead, which will resize your image with the slider: