I don't know exactly how this works, but it looks like a good fix to me, so committing.
if ($fields[1] == "student") {
- if ($teachers = get_users_by_capability($context, 'moodle/course:update', 'u.*,ra.hidden', 'sortorder ASC')) {
+ if ($teachers = get_users_by_capability($context, 'moodle/course:update', 'u.*,ra.hidden', 'ra.sortorder ASC')) {
foreach ($teachers as $u) {
if (!$u->hidden || has_capability('moodle/role:viewhiddenassigns', $context)) {
$teacher = $u;