To purchase your argument, I would have to conclude this applies to Einstein's 1918 solution to the traditional solution of the twins experiment. However, Einstein proved all parties agreed on the solution.
Now, in my case, we have a solution and the twin's know the answer.
Yet, when I ask SR, you and SR claims well now the answer depends.
Guess what, no it does not, the twins have the answer. It is just that SR cannnot decide it.
So, we cannot trust SR.
Oh, you mean the twin paradox? All observers will agree upon the ages of the twins only when they coincide in the same place for a direct comparison. Since the twins are separated by some distance in the new frame in your scenario, simultaneity effects come into play over that distance between them as viewed from other frames. Now, if you can put the twins together in one place in the new frame, then all observers will agree on the ages, as they can do a direct side by side comparison with no simultaneity effects involved.