Could it happen in a leg with U-Turn that one team, completing all tasks and arriving at the pitstop, just fails to find the U-Turn board midway? I mean, due to the route the taxi driver chooses, the team may just take a shortcut or make a much longer distance and hence the team members don't see the U-Turn board as if it didn't exist in this leg and go directly to the next task locale.
The way the race course is structured in the US version, it's almost impossible to skip the U-Turn board since 1) the clue says to visit the board, and 2) their next clue is usually right beside the U-Turn board. And even if they skip it because they failed to see it within a few feet of them, they would probably be turned away from the pit stop since they missed a route marker or be penalized. This is especially the case if the team who accidentally skipped the U-Turn in actually U-Turned.
In other versions however (like Philippines 2), there is no clue next to the must-vote U-Turn or Yield boards. Instead, the clue that says where the U-Turn board is also says their next destination, only that the teams have to pass by the U-Turn board first. For example, Charlie & Daniel in Philippines 2 forgot to visit the U-Turn board in Leg 2, only to realize it after arriving at their next clue in another province. They went back and discovered they were U-Turned, which they had to do before returning to the race course.
Is there a penalty for ripping off the clue?
According to the promo of EP6 of TAR China (Shenzhen version), a team member does so because he's very angry.
What does "ripping off a clue" mean? If you mean destroying their own clue, I think the team won't get a penalty since destroying their clue would be to their own disadvantage, similar to losing their clue or giving it away. Getting a second clue would institute a penalty, however.