Reading your messages again, i saw this:
Culture 7 being made of some students from G1, G2 and G3.
I also saw you use "G1" and "Y1 Culture 1" the activities. that is "stupid" since both are the same!
So i guess you misunderstood how to make subgroups.
Please check the attached file and check how i done subgroups for G1, G2, G3 and Cultures7.
Or, instead of "Cultures7" just add G1, G2 and G3 into the activity.
I fear a bit that your students set is not finished yet. You should use the automatic split feature, since it will be more complicated if you have more of those "problems".
Or import the students structure by csv.