Magnetic oscillations permeating the solar atmosphere can be altered by flares. This could be due to changes in the atmospheric magnetic waveguide, the thermodynamic stratification, or both. To investigate this, we examine oscillations in a magnetic pore crossed in part by the ribbon of a C8.2 flare, using observations from the SUNRISE Ultraviolet Spectropolarimeter and Imager (SUSI) aboard SUNRISE III. We track the core intensities of eight spectral lines between 327--329 nm and show that oscillatory power in the 4.2--7.0 mHz range, measured around 30 minutes after the flare peak, exceeds the preevent value in all eight lines by factors of 1.60--8.71. Conversely, in the 7.0--11.5 mHz band, the postevent intensity power is lower---approximately 0.13--0.41 of the original power in seven of the observed lines. Line-center velocity measurements support the lower-frequency enhancement. This delayed, line-dependent shift toward the lower-frequency band is consistent with flare-induced changes in wave transmission, reflection, or resonant response, although thermodynamic and magnetic effects cannot yet be separated.