There’s not much we can do without a link since we would definitely need to see one in order to know what’s going on. Otherwise there’s no way to know.
The only thing I can say is to double check your slider settings. You probably just have the width still set to 920px when it should be 1140px or whatever you need it to be. Also, use a plugin called Regenerate Thumbnails anytime you change the size of your image settings throughout your theme.
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