I can see the problem on your site, and examining the page source in Firefox I can see that the problem arises because the width is not set correctly on the slider container (it is calculated by JavaScript, and for some reason it is being calculated incorrectly).
I have tried to reproduce the problem on my own test site, but cannot, so it appears to be something particular to your site.
As this is a staging site, is it possible to check the issue when all non-Toolset plugins are disabled and the theme is switched to a default theme like twentytwentyone?
Does the problem still occur? If not, it should be possible to infer the source of any conflict by a process of elimination.