I confess that you might possibly be talking about me. (Or different groups just happened to have the same thing happening.)

I didn't tell my groupmates this, but I had little idea what was going on, so couldn't get stuff done. I also didn't want the Supervisor and postdoc to know that I had little idea what was going on and pull down the entire group (the group gave the impression that they didn't want the postdoc and Supervisor to know too) so I kept quiet during meetings. There is a popular saying: "Better to remain silent and be thought a fool than to speak and to remove all doubt."

In any case, in the Peer Review I gave myself -10% contribution and all other three groupmates +10% contribution. Might not be sufficient for justice but that's what I did.