Lightbox is sliding down half the page when first opened

Site URL: https://brooksreynolds.com/photo2

Working on building a new portfolio and was messing around with layouts. Think I'm happy with how it looks but when I scroll down a few rows and then click a photo to open it in a lightbox, the lightbox opens then slides down half the page. How do I stop this from happening?

It sounds similar to this

https://forum.squarespace.com/topic/324364-squarespace-lightbox-new-padding/#comment-812529