On the web, or in one of the apps?
If I attempt this one, where the solution is O-O-O, it seems fine. (?)
http://www.chess.com/tactics/?id=39915
Castling in tactics trainer
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How come that a 1700 Blitz player has a 3200 Tactics Trainer rating???
I mentioned this a couple of years ago and it is still true. Every puzzle in which castling is the first correct move generates a fail message as soon as I castle.