Hello SMcClure,
Thank you for your question about the edge of the previous image showing on the edge of the current image. That behavior is also there on the default images, so it is not due to your images, it is simply the default design of the gallery.
I am working with the Bold Grid Primas Theme, and the slideshow at the top of the page shows the edge of the previous picture. I replaced the stock photos with images the exact same size. I even tried a larger size photo with the same result. Is there a way to fix this so the pictures align properly, or is this the way the slideshow works?
I ran into this issue with this theme today. This has been taken care of and will be in the next release of the theme. In case anyone runs into this problem and references here, the image can be adjusted to the middle with CSS using the CSS tool in the customizer: