I found two problems that are identical, except for the FEN notation on one is (probably) incorrect.   One allows for castling, while the other one does not.  I could not find the game itself in any databases to verify this though.

The two tactics are #0020871  (The seemingly correct one) and #0024504 (The one that does not account for castling)

The ability to castle does not change the correct line of the tactic, only makes the second best line able to hold a draw.  Thanks for making an amazing site!

u da man, big dog.

-li'l dog

Also problems 0021425, 0022065, and 0025410 are all the same.  Credit to Igor Randjelovic for finding them.  Problem 0021425 seems to have the best information in the source data.  It includes the players names and the event.

Beyond the specific problems you point out, no one running the site has yet to answer my simple and more fundamental question of why castling options are not given when you work a problem (as they are at chesstempo, e.g.)??

There is actually a really crappy problem on TT that the answer is castling queenside, but there are hardly any pieces left on the board.  Just a nasty trick of a puzzle.  It seems like it would make sense, and I have honestly tried castling on a problem, but since it was not an option, was allowed another guess.