You can try resolving this issue by adding the following CSS code in the Custom CSS code option of your theme on the below path.

Admin Area -> Appearance -> Theme Settings -> Custom Code -> CSS Code

body.single-oferta .sh-gallery-item:hover .sh-overlay-style1 {
    opacity: 1!important;
}

body.single-oferta .sh-gallery-item:hover .sh-overlay-style1 .sh-overlay-item:last-child {
    display: block;
    opacity: 1;
    height: 100%;
}