Why is the wrong product variant showing up in the cart?

[Amplifier]

Hi there, 

Hoping can get an answer to my problem. When customers select a Large size for example on the product page of any of our apparel then click add to cart but when they view the product in the cart the product it displays the wrong size.

here's the link to the store: https://store.amplifier.org/collections/apparel

We are using a custom theme based off of the Debut theme version 3.1.1.

Thank you,

Isabella