The teacher should occasionally intervene in the process if the tasks haven't managed to keep the team members together. (Emerson et al, 1997).
The best advice is to guide the team and to let the team resolve their differences independently. Direct intervention requires private meetings with students, with the teacher describing the observed behavior and asking them to make some changes. The teacher can also take the team into his office and discuss the situation to create solutions. Someone should be reassigned to another team only when a solution can't be found. Learning how to resolve group conflicts is part of a successful group's dynamics. Changing a team's members is not a helpful strategy and it can break the balance in the team. When students ask to be swapped, the teachers should warn about a "goodbye" or "divorce" where the team members formally discuss the reasons why there is a problem with that person. The student is responsible for finding a new team.
The teachers should remind the students that conflict can be helpful and can prepare them for similar situations they may have to face in their professional life. Negotiation skills are part of the learning they acquire in GL activities. Groups become stronger when they learn to resolve their differences. Teachers can identify the team's problems by monitoring their progress through reports, group homework, etc. When stating that he's confident about the teams being able to resolve their differences, the teacher will be inspiring confidence in them as well.