S17 - Gary and Mallory got lost for hours in Oman and still arrived minutes behind Nat & Kat; had they gotten lost for ~30 min less, we would have lost those girls. And once again in the finale, Jill & Thomas were trailing behind them until they took some bad directions and fell behind Brook and Claire.
S18 - Gary and Mallory got an incredibly bad taxi in the finale, and even then they managed to get to the final task with the other two teams still there; they had a solid chance at winning, taken by something out of their control.
S25 - That twist came in clutch, and the memory task seems to be the team-killer of so many seasons; it gave Amy & Maya the win, and it crushed teams like Jaime & Cara in S14 and Raquel & Cayla in S33
Now, I don't want to discredit the win of these teams, Nat & Kat were still ahead of Jill & Thomas in the finale and Kisha and Jen still beat the Globetrotters despite never winning a leg, my point is that casting professional athletes and strong women does not guarantee a win, navigation skills are important, so is attention to detail and many other attributes, you can see this pattern in many M/F and M/M teams as well, the race rarely comes down pure physical.