I have a date field, among others, inside a content multigroup. I enter one group and fill in the date, then create a second, empty group, then delete that empty group and save the node. On the view page, the date for group 1 is empty, and that date has jumped down to the second group (even though that second group was deleted).
I've attached a screenshot that shows what I'm talking about. It seems to only be happening with the date field.