Featured slider height issue

Hi, Working on a site with Rock Star, I notice that the featured slider (showing pages) has a weird issue with the height of the slider elements. After fist load, the space for the slider seems much too high, making the forward/back buttons and the dots (at the bottom) to be placed too low. Only after all slides have passed and the slider goes back to the fist slide, or if the browser window size is changed, the height gets adjusted to fit the slide images. This seems to happen on Chrome and Firefox, I've not tested other browsers. No idea if this is related to a particular theme setting but when I switch to the Demo slider content, the issue is gone. And what also strikes me as odd, is that the demo slides are correctly adapted to the window height, unlike the custom page featured images even though they have the same original 1920x1080 dimensions... Please see http://dustbindev.aufildudoux.net (I set slide delay to 0 for easier debugging) What's going wrong?