I took a look at your SR. With Harmonic Balance, use spline or linear interpolation. Causality correction should be set to fmax. (auto takes forever and only should be used only if fmax doesn't work.) If the data is non-causal, you *want* causality correction! The same goes for passivity. I always turn on passivity checking ...and if the data is non-passive, then I set passivity to enforce. If the data is passive, then I turn passivity checking off.
If you follow the guidelines in the nport appNote, you will be fine. Without seeing your s-parameter data, it is difficult to give more solid advice. (I'm the appNote author and worked with R&D on the most recent update for MMSIM 11.1).
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Cadence Design Systems, Inc.