I am attempting to setup a simulation, of a hoop shaped part, that I have cut up into a pie shaped piece for analysis.   The problem is that when I go to setup a symmetry fixture, on each side of the pie shaped cut, I get an error message (the plane of symmetry for this restraint is not perpendicular ...) , and cannot establish the fixture.   

The strange part about this is that the exact same symmetry fixture worked fine in Simulation 2011.   I even opened up one of the simulations from 2011, in Simulation 2013, and symmetry fixtures appear fine, with no errors.   But if I edit one of those symmetry fixtures, deleting the two surface selections in the fixture, and then re-selecting those very same surfaces, it gives me the error message, and won’t let me do it!

Now I just set up the simplest of pie shaped parts (envision a pie with a hole in center, then sliced), and I cannot put symmetry fixtures on both cut faces of a slice.   Unlike this simplified test model, the real part cannot be modeled with 2D simplification.  And I don't think that just putting on flat face fixtures will make this function as if it was a continuous 360 degree hoop. (image attached)

Any insight on how to work around this would be appreciated!