[pescetom]

I think this belongs in Simple Rulings even though it takes some explanation and caused some discussion.
Follow your local regulations and your own judgement, but please point both out.

In a club f2f MP tournament with Howell movement, Bill and Sue move to EW knowing they will face Mike and Jane, boards 9+10.
Jane arrives and sits in South and places the first board on the table.
Bill and Sue make 3♥-1, which looks to them like a good score given that NS have spades, maybe game.
Jane tries to enter the score but the lead is flagged as wrong, realises she is scoring board 9 but this is board 17.
Director is called.
Turns out Mike and Jane already played this board two rounds ago but in EW, making 4♥-1.

Boards 9+10 are located and duly played.
But later Bill and Sue are due to play boards 17-18 in EW against Sally and Tom.
Director awards Sally and Tom 60% for board 17, but what should she award Bill and Sue? See poll.

Please explain and justify your choice, in particular if you were willing to award not played or if you prefer to let Bill and Sue maintain the (joint top) score obtained against Mike and Jane even though the latter pair had already played the same board obtaining much the same score.

[barmar]

Since Bill and Sue played the board, they should normally get the score they achieved on it. However, the director can adjust if they think the defense had an advantage because they'd already seen the board -- they theoretically can defend double dummy. But if they didn't realize they were playing a board they already played, they probably couldn't work this out, so there's no actual damage.

[CMOTDib]

I voted other.
The reasoning is that Mike and Jane had previously played the board and therefore Law15 B 1 & 3 seem to be appropriate. I believe that "cancelled" in this context means that the play between Mike/Jane and Bill/Sue never happened. At Law 12 C 2(a) it is suggested that the score should be 40% if directly at fault, 50% if partly at fault or 60% if in no way at fault. The narrative would suggest that Bill/Sue knew that they should play boards 9 & 10 but it seems they accepted that Jane knew what she was doing and played the board without discussion. It seems to me that they are partly at fault for playing board 17 and therefore they should have an artificially adjusted score of 50%. I might reconsider if we know that Bill/Sue are inexperienced and Mike/Jane say that they convinced Bill/Sue to play the board on the table (stopped them calling the director).
It might be appropriate to discuss the situation with Mike/Jane and look at procedures (table cards or scoring equipment) to see if this could have been prevented.