Stop Product Page Skipping To Second Image instead of Featured Image

[Ruby023]

I'm using the Sense theme. When a customer clicks on a product, the first variant is automatically selected and thus the image changes to that rather than the featured image. Is there any way around this so as to keep the featured image showing until a variant is manually selected? 

https://hanksyarnparlour.com/

[Ruby023]

I'm using the sense theme. Any idea where I would find the specific code in this theme?