That is not normal, there is definitely a problem with the server you are running the website on it. I am assuming that you are previewing in a browser, in some cases, when you preview a Muse website in a browser, the link you are previewing cannot be refreshed or accessed after about 10 seconds or so (This is not about a specific widget, in general about any site we preview in Muse).
To get the right result, since the Page Slider needs all the pages to be presented in order to run, either publish online or export as HTML and check the outcome. This is only in cases where you have a problem like what you mentioned, basically, there should be any waiting issue even in previewing, but if you publish the site, it will run with no speed issue at all.
If you still have the issue after publishing the site, submit a support ticket and let us know the URL, we will be more than happy to fix it for you.