Hello,
The “Cover” size for the bg image can cut some parts of the image. So this is not something caused by our theme, that CSS property works in such a way. Either use the “Contain” property or upload the image that will look better with the “Cover” option.
cover
Scales the image (while preserving its ratio) to the smallest possible size to fill the container (that is: both its height and width completely cover the container), leaving no empty space. If the proportions of the background differ from the element, the image is cropped either vertically or horizontally.
Here you can check each bg image size – https://developer.mozilla.org/en-US/docs/Web/CSS/background-size
Kind Regards