Mobile 2 product grid - grid changes when adding to cart

Site URL: https://www.birdtrickstoys.com/

Hello!

On mobile, when you click "add to cart" it will change the size of the product grid. This pushes other products off screen. 

I've made a copy of the site removing all CSS besides the product grid, but it still resizes whichever column the product was in. 

Any help would be greatly appreciated! Please let me know if more info is needed. I've attached a screen recording of it happening on the main site on mobile. 

Thank you,
Hannah

Edit to add, the code for the grid I'm using is:
            /* MOBILE PRODUCT GRID */
@media only screen and (max-width:767px) {
.products .list-grid {
display: flex;
flex-wrap: wrap;
justify-content: space-between;
}
.products .grid-item {
width: 48%;
}
}
@media screen and (max-width: 767px ) {
    .products.collection-content-wrapper .list-grid {
        display:grid !important;
        grid-template-columns: 1fr 1fr !important;
    }
    .products.collection-content-wrapper .grid-item {
        width: 100% !important;
    }
}

Use this code to Custom CSS to fix problem

@media screen and (max-width:767px) {
div.grid-item {
    min-width: unset !important;
}
}