I just updated to the latest version of MB Group (from 3.1.18). I had clonable group fields already existing.
First, when I updated, I got a warning that 'clone_empty_start' was not a valid array key (group-field.php line 220) so I had to go through all my cloneable fields and add that option in.
More importantly, I am now having a problem where an empty group of fields is being prepended to my groups with a number of 0 (in the group title). This is happening whether I set 'clone_empty_start' to true or false.
If I save the item, ANOTHER empty group of fields is added. So now I have Group 0 and Group 1 which are both blank, and THEN my previously-saved values start with Group 2.