Hi,
I think this are the missing lines in the file fields.php in the translation en_us:
'field ProjectTasks repeat_by' => 'Repeat by',
'field ProjectTasks repeat_d' => 'Repeat day',
'field ProjectTasks repeat_end' => 'Repeat end',
'field ProjectTasks repeat_forever'=> 'Repeat forever',
'field ProjectTasks repeat_m' => 'Repeat month',
'field ProjectTasks repeat_num' => 'Repeat number',
'field ProjectTasks repeat_y' => 'Repeat year',
After add these lines you can translate it in your own language by using the translation tools