We had the same issues. sometimes A seeing B,C,D and B seeing C,D,F and so forth. A real mix where we never got the complete group to see the complete group. Alls the trouble shooting did not work for us, so we actually switched to a different voice and video platform. Since then we are very happy :) If there is a real solution for this in Roll20 though it would be much nicer, as it does not cramp up the scace with the extra video feeds so much.