missing outcomes related strings in gradebook

error message below:

Help title string does not exist: [aggregateoutcomes, grade]

• line 483 of /lib/outputcomponents.php: call to debugging()
• line 1556 of /lib/outputrenderers.php: call to help_icon->diag_strings()
• line 905 of /grade/edit/tree/lib.php: call to core_renderer->help_icon()
• line 92 of /grade/edit/tree/lib.php: call to grade_edit_tree_column_aggregateoutcomes->get_header_cell()
• line 151 of /grade/edit/tree/index.php: call to grade_edit_tree->__construct()

Help contents string does not exist: [aggregateoutcomes_help, grade]

• line 486 of /lib/outputcomponents.php: call to debugging()
• line 1556 of /lib/outputrenderers.php: call to help_icon->diag_strings()
• line 905 of /grade/edit/tree/lib.php: call to core_renderer->help_icon()
• line 92 of /grade/edit/tree/lib.php: call to grade_edit_tree_column_aggregateoutcomes->get_header_cell()
• line 151 of /grade/edit/tree/index.php: call to grade_edit_tree->__construct()

Invalid get_string() identifier: 'aggregateoutcomes' or component 'grade'

• line 5982 of /lib/moodlelib.php: call to debugging()
• line 6536 of /lib/moodlelib.php: call to core_string_manager->get_string()
• line 1576 of /lib/outputrenderers.php: call to get_string()
• line 67 of /lib/outputrenderers.php: call to core_renderer->render_help_icon()
• line 1562 of /lib/outputrenderers.php: call to renderer_base->render()
• line 905 of /grade/edit/tree/lib.php: call to core_renderer->help_icon()
• line 92 of /grade/edit/tree/lib.php: call to grade_edit_tree_column_aggregateoutcomes->get_header_cell()
• line 151 of /grade/edit/tree/index.php: call to grade_edit_tree->__construct()