The default is not neutral
Leaving teams to form themselves looks fair because everyone gets a choice. In practice it favours students who already have a network. International students, commuters, anyone new to the cohort, and quieter students tend to be picked last or left to take whatever is left.
Spot it before it happens
By the time a struggling team shows up in your inbox, the term is often half over. The cheaper intervention is at formation: make sure no team is stacked against itself, and that nobody lands in a group with no shared availability.
Design the process, not the policing
You do not need to micromanage teams to make group work fairer. You need a formation step that already accounts for who tends to get overlooked, so the fix is built in rather than chased down later.