This is really weird issue. I can see the slider script is calculating the height of the slider wrong way. This works perfectly fine for me and you are the only one experiencing such issue.
As you say you’ve disabled the plugins and the issue persists, my question would be what hosting do you use? Do you use some caching on your server? If so, please try to flush the cache to see if that helps.
As a workaround, you might temporarily use this custom CSS: