Don't get me started on group work! So many assessment issues here--how does one assign individuals grades on work done by the group? Group work only makes sense under very special circumstances, the first of which is that learning to work in groups is an official objective of the course--not just done because instructor wants to cut # of papers to mark by factor of five
Negative outcomes of group work: preventing good students getting scholarship by placing them with weaker students; (b) encouraging biases against minorities, disabled, and unpopular students by letting students choose own groups; (c) exaggerating gender politics (e.g. males do most of the talking in small group discussions where no instructor to moderate; women delegated 'secretarial' roles, etc); (d) allowing weak students to sneak through on the backs of other student's work; (e) encouraging academic misconduct: students sign project submissions to which they did not in fact contribute.
It is unusual for everyone to contribute equally, and even less likely that everyone will perceive that everyone contributed equally.
If you insist on doing group work, what assessments are you doing to evaluate whether group work is achieving the claimed benefits? How are you assessing things like "collaboration" or "teamwork"? If you are not assessing or even monitoring these characteristics, you cannot claim these benefits. Because the outcomes pictured above are as likely as those benefits being claimed. If you are going to claim a benefit, be prepared to document it. (Teachers, like doctors, should have take an oath to 'do no harm'. Without careful monitoring, group work probably does much more harm than good.)