Hello, Steve.li.vt,
We apologize for the delay in responding.
Please do the next test – change all code in your child theme/style.css to
.swiper-container.swiper-control-bottom.second-initialized li.thumbnail-item.active-thumbnail {
border: blue solid 5px;
}and check how the border on the last thumbnail in the gallery works. You will get a blue border that appears after 1 click.
It means that the problem is caused by your custom styles, as was already mentioned.
We strive to provide excellent service to our customers, but please be advised that we are not responsible for custom code in your child theme.
Kind Regards,
8theme team