Hi, you need to modify the helper file : Helper/MinifrontpageproHelper.php
at line 197 you will see this code :
if (!empty($images->image_intro) ) {
$orig_image = $images->image_intro;
} elseif (empty($images->image_intro) && !empty($images->image_fulltext) ) {
$orig_image = $images->image_fulltext;
change that to :
if (!empty($images->image_fulltext) ) {
$orig_image = $images->image_fulltext;
} elseif (empty($images->image_fulltext) && !empty($images->image_intro) ) {
$orig_image = $images->image_intro;
Please note this modification is not an update safe, so it will be re-apply it everytime you install a new update.