Help! Leaflet (HTML, javascript) only shows top half of image at all zoom levels

Leaflet has been set up to display tiles made from an image file sized 8196 x 4750 pixels. Tiles are available for Zoom levels 0, 1, 2, 3, and 4. Zoom level 0 has two tiles. Leaflet only shows one tile (the top tile) even when it is dragged off the top edge of its display window and the other tile should automatically load in the opened space. Zoom level 1 shows the same half of the image, this time made up of several tiles. Similar for Zoom levels 2, 3, and 4 - the same half-image is shown, each made of many tiles, with the lower half of the image missing. What can you do to get Leaflet to load the full image? I have tried to add setInterval(function () { [login to view URL](); }, 5000); as suggested at various websites. Did I code this wrong? I made my own tiles. Did I make them incorrectly, or have I not included some additional file needed by Leaflet? I attach: (a) the original large image; (b) the set of tiles made from that image; (c) an HTML file that displays the tiles using Leaflet; and I describe here basic instructions on how to use these files to observe my concern with Leaflet. You can use your own resources to create tiles from the large original image if you think my set of tile files are incorrect or incomplete. You can see the HTML and javascript used to show Leaflet in operation and behaving badly. You should want to have experience specifically with Leaflet because the only concern is to get Leaflet to display the full image at all Zoom levels. If you are not facile with Leaflet this may not be an opportunity for you. My request is very specific and I seek a very specific solution. I attach files. Make a folder, download the "tiles" compressed file and extract it there. Download the HTML file in that same folder. And download the large, whole, image so you can know how a full image should look (and so you can generate your own tiles if that's what you choose to do). The HTML file will for the tiles in the same folder. Let me know if you need help with this. Do you have questions or comments? Have a look at the files and get back to me!