> a subset of teams get paired dispropotionally often in UEFA Champions League when compared to random

To the point they have rules that prevent the same game from being played by two teams in the same home stadium for 3 straight years. Not sure how they handle this. Do they just redraw if that pairing is drawn, do the hold back one of the team's ball from the bag, or do they manually set one of the teams against another from the pool before drawing the remaining?