Twin U-turns: One U-turn before the detour, another U-turn after the detour.
The team U-turned before the detour must perform both tasks before proceeding to their next location, the location of the 2nd U-turn, which means they can only use the 2nd U-turn (if still unused) after finishing both detours. Meanwhile, if a team is U-turned on the 2nd one while the 1st one was unused, the team will not be allowed to backtrack in order to use the 1st U-turn.
Good idea? Bad idea?