My S21 and Eigenmode simulations disagree HFSS

Hi all, I'm having a problem in ansys where I have a quarter wavelength resonator (with a target frequency of 7.0 GHz, inductively coupled to a transmission line.)

When I do eigenmode analysis, I get 6.99 GHz for the resonator mode, which is what I expect.

However, when I do a driven modal scattering simulation, I get an S21 (dB) dip at 12.63 GHz and nothing at 7.0 GHz

I've even tried to narrow the simulation window to the interval f=(4 GHz, 9 GHz), and still don't see anything happening at 7.0 GHz. What could be going wrong here?

Any insight/help is greatly appreciated. Thanks.

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