From what I understand, these puzzles are taken from actual games of people. Sometimes, there are calculated sequences that have two winning solutions as per move by move basis. OR the move I chose I is not what the person actually played, hence I am considered "wrong" when it is objectively a weaker move.
This is an awesome site and I understand that this is a massive undertaking, but are these puzzles being ran through Stockfish or so?
Puzzles only have one correct option.
Give examples or stop crying
A good tactic to use is that if you think the puzzle has more than one solution is to load the game up with Stockfish 8 in the browser analysis board and try to play the game out against the engine.
If your move gives you the same ending evaluation as the puzzle's correct choice, then your puzzle indeed has multiple solutions.
Some puzzles take into account that there are multiple solutions (using the queen vs rook to checkmate for example)
If your puzzle doesn't include your solution despite being validated, that would be an interesting forum post, share it and we'd love to discuss it!
Sometimes, you think some puzzles makes no sense, but when you dig in it, you realize it's actually correct
Sometimes correct, sometimes no :)