I have had students do 180 degree turns after finding that their teacher actually believed they could do it and then that individual became instead of the class troublemaker, the most dedicated student in the class. On the other spectrum, I get the students who don t care, don t want to care, and just want to be done with it and nothing that I or her or his group members say seems to change that. I guess overall, my strategy has been to work on the individuals first and then work on the group for serious problems and the reverse for less serious items. If necessary, I try to facilitate a problem solving session to get the parties to agree to a new plan of action. I often did not find out about these problems till very late.
Students are reluctant to complain about each other.
Usually the intervention was successful. I change groups regularly. I give group tests where cooperation and smooth functioning are necessary. Problems seem to work themselves out given time. I reform groups and allow students to work out problems themselves.