Take tactic #0044551 for an example. There is no way that is a 1200 rated problem. The 10% pass rate will attest to that. My theory is that partially correct solutions affect the rating of the problem while the high failure rate assures that players not ready for the problem are the ones getting it.

I'm not sure what the fix would be, but I have encountered this more than a few times.

Edit: To clarify my thesis: partially correct solutions reduce or eliminate the change in rating even though the players rarely get the problem right, so the rating never moves higher.

Bump.

I have to agree with you, on this problem.

Almost everybody will find the 1st 4 moves, without having a clue about the surprise ending, and end up with a positive score. (myself included!)

I have wondered about this as well, I have seen 6 or 7 % solve rates for 1800 problems, and wondered why they were not rated higher. But you hit the nail on the head, I think.

Sorry, I'm going to bump this on more time.