If the subject of the problem will two-box if he sees the big box has the million dollars, but will one-box if he sees the big box is empty. Then there is no action Omega could take to satisfy the conditions of the problem.

In this case the paradox lies within having made a false statement about Omega, not about TDT. In other words, it's not a problem with the decision theory, but a problem with what we supposedly believe about Omega.

But yes, whenever you suppose that the agent can observe an effect of its decision before making that decision, there must be given a consistent account of how Omega simulates possible versions of you that see different versions of your own decision, and on that basis selects at least one consistent version to show you. In general, I think, maximizing may require choosing among possible strategies for sets of conditional responses. And this indeed intersects with some of the open issues in TDT and UDT.

This is what I was alluding to by saying, "The exact details here will depend on how I believe the simulator chose to tell me this".