It seems to be an issue with MySQL wich is possible to ignore by adding the following code. Just create a module and add a hook_views_query_alter in your module:
function yourmodulename_views_query_alter(&$view, &$query) {
// Find all combine fields and make them case insensitive.
foreach ($query->where as $group_key => $group) {
foreach ($group['conditions'] as $key => $condition) {
if (is_string($condition[‘field’]) && (preg_match(‘/:views_combine/’, $condition[‘field’]))) {
$query->where[$group_key][‘conditions’][$key][‘field’] = $condition[‘field’] . ‘ COLLATE utf8_general_ci’;
}
}
}
}
More info can be found on:
Hands on with digital technology 