Ever since switching to Coppermine 1.15, they removed the full path on batch add, which may be better server wise on long names, but when you have to add files the risk of selecting the wrong album is 300% more certain. So here’s your fix.

Open include/functions.inc.php and find this line
$options .= '' . $LINEBREAK;

Change the whole line with this instead
$elements = array();
foreach ($cats as $cat) {
$elements[] = $cat['name'];
$options .= '' . $LINEBREAK;

Please Note: this is based on a tutorial from coppermine forum which I can no longer locate on there