Fix Shopify Sticky Product Image with thumbnails

My product pages on Shopify are meant to keep the main photo locked in view while a visitor scrolls through the description and variants, yet on this page – https://gyftalala.com/products/anniversary-splashbook – the image simply scrolls away. I’m not sure which code snippets might be overriding the expected “position: sticky” behaviour.

What I need
• Diagnose why the product image with thumbnails fails to stay fixed.
• Require the image to remains visible (stay fixed in place) throughout the scroll until it naturally hands off at the end of the product section.
• Keep the solution lightweight, theme-update safe and doesn't affect any other code.
• Provide a short note of the change locations.

If additional theme or app conflicts appear, outline them before proceeding so I can decide whether to remove or adjust those elements.