Hi there,
the issue is the default Woo templates uses floats – you can use this CSS to force all the products to the same height to fix this:
@media (max-width: 768px) {
.woocommerce[class*=columns-] ul.products li.product:not(.product-category) {
min-height: 350px;
}
}
In GP Premium 1.8 this issue should be resolved as we have implemented CSS Grid for displaying them.