Puzzle doesn't accept solution for a rare reason

@Cellini As far as I understand, the solution proposed by the OP is perfectly valid for the puzzle as it leads to a checkmate in the same number of moves as the "approved" one. Unfortunately, OP's solution is considered wrong because, in the actual game, it would lead to a previously occurred position for the third time, resulting in a draw.

Puzzle solvers have no way to infer what positions have already occurred in the game a puzzle is taken from, which means that the puzzle in question should either be "fixed" (e.g. by making sure the system accepts the equally valid alternate solution) or removed from the pool.

№ 11,

Puzzle solvers have no way to infer what positions have already occurred in the game a puzzle is taken from[.]

FWIW, you can actually replay the whole game to the puzzle position (by clicking the movelist on the right, or using your mousewheel / arrowkeys). But I understand it would be silly to expect people to do that. 😅

@pawnedge That is true, I stand corrected: by inspecting the game, the solver can actually see that one of the moves could lead to a draw by repetition. This doesn't apply to the "storm" mode, though.

I played a game recently where Stockfish 9 gave me the wrong suggestion for a move. I had force mate in 3, but it somehow missed the first move (in both of it's suggestions). I was baffled.