I think that is because of the way you have set up your site’s optimization (not within Photonic). The slideshow script was updated to its new version in the latest Photonic release. Within Photonic, I use a technique called “cache busting”, to ensure that you are getting the latest version of the JS files. This is done by including scripts this way:
<script type="text/javascript" src="https://example.com/wp/wp-content/plugins/photonic/include/ext/splide/splide.min.js?ver=4.1.4-20230514-213448" id="splide-js"></script>
However, on your site, you have something that strips out the ?ver=xxx
and makes the URL look like this:
<script src="https://leafext.de/wp-content/plugins/photonic/include/ext/splide/splide.min.js" id="splide-js"></script>
This often causes browsers to load the older version of the file, and it would appear as though the script is not working.