Thank you for an awesome theme!
As a beginner I´m having a bit of difficutly with featured post pictures shown in the slider. While they work great on my computer screen, the animation totally bugs the slider on mobile devices (as well as the customizer preview). I have kept the standard slider size of 1200 x 500 px and I´m also using same-sized pictures in the posts.
The theme registers different image sized for the featured and slider images. If the files you are using are larger than both configured size (slider and featured) and are also the same aspect ratio between them, the generated slides should be of the same size.