I agree with you guys Tom and Matt should have been given a penalty. But the whole RB was poorly planned for me. It's not logical to fail the RB if you don't hit the target with the 40 arrows. Maybe a team should be given a 30min penalty-waiting period and then allowed to continue the race.
On another note, although it was not obvious, the teams lost a lot of times in taxi moving back and forth. I was in Prague last summer so I realized that the most part of the episode was around the main square but they were approaching from all different sites. Their first destination was the cluebox in front of the tower, if they want through the arch in 5 min they would have been to the square where was the knight detour and another 5 min from the square is the Charles Bridge. Instead they made a whole circle with the taxi to bypass the square and end up to the bridge and then came back to the square.
As for the end the reason that Dave and kelly lost two places is because they went by foot to the castle, which is on the opposite side of Charles bridge but on a high hill, which takes some time to reach it. So they approached the Castle by the back side while the taxis took the others on the front side where the main gate is.
The shots we saw from David and Kelly was from inside the castle while Grant was waiting just outside.