I would not use device-width. Since I cannot see your media queries, I would say that that is your issue. Responsive design is device agnostic and using device-width is almost anti-responsive - since you are designing for that device width.
Instead, use max-width and min-width if you have to. Shrink your browser window, when it breaks your site - you have your break point. Fix that and then shrink again. This method of using the max-width then will be more consistent irrespective of the device, orientation or pixel density.
Using max-device-width is just a rabbit trail of getting specific with orientation and pixel density etc..