RE the group assignments, my university quite successfully dealt with this by introducing a scaling factor based on peer assessments within the group. This scaling factor was strong enough to allow a group to fail one member if they received poor enough grades. Failing one member tends to boost your own grade as well, as the assumption is that you ended up having to pick up the slack.

I did three group assessments, and out of those three failed two students with the help of my teammates, by co-ordinating our peer assessment. This peer assessment does not become public until grades come out, at which point they can be disputed. But 3 vs 1 usually comes out in favour of the group.