Gallery glitch

My photo gallery displays the thumbnails for my selected images perfectly, but when I click on an image to look at it, the order of the full size pics is wrong, and it includes images that are not part of my gallery.

You can see the problem on this page by clicking on the top left thumbnail, and then clicking “previous” on the image page. It then takes you through a collection of all the graphic files on my website:

https://www.calzoneandanvil.com/about/history-in-photos/

Any idea why either of these issues would be happening?