Hi @Ryan thank you very much for your feedback.
I tested the app in incognito using Mozilla Firefox, Microsoft Edge and Google Chrome.
With all the 3 browsers, the zoom tool slider works for the first 3-4 photos. If I continue to browse the photos, or move to another picture using one of the points on the map, the slider stops to work.
A curious behaviour in Microsoft Edge and Google Chrome is that the download tool in these 2 browser apparently downloads a JPG, but if I open the file I discover that it's a PNG renamed with JPG extension.
Maybe also in your test the picture file is a PNG renamed with JPG extension: take a look please.