Everything displays properly until I add the 57th jpeg. Then the ‘Captions’, ‘Counter’, ‘Prev’, & ‘Next’ disappear. Those ‘Parts’ are supposed to display on the bottom ‘Padding’. First 2 picture the result with 56 jpegs. The 3rd & 4th picture the result after adding just 1 more jpeg.
Did you try to place the lightbox and the text elements (Prev/Next/Caption, …) away from your page area to the left of your canvas? (This won‘t influence the centered appearance in browser view.)