That's how CB Gallery is designed. Have added a feature ticket to review always displaying details for certain gallery types (basically ones that can't provide a thumbnail). For now your only option is to alter the CSS as follows.
Code:
.cb_template .galleryItemsContainer .galleryContainer .galleryContainerBottom {
opacity: 1;
}
That should work fine if added to CB template CSS override usage. Note it's not possible to specifically target file media so this will cause the footer to display on photos as well.
forge.joomlapolis.com/issues/6692