*** ERROR # 410 *** Specifying lower bound in EIGRL card may compromise RESVEC quality. Subcase ID 1 EIGRL ID 3. *** Run terminated because of error(s) in the input data.

Your EIGRL has a V1 (lower frequency) set to 300.0

Modal FRF analysis uses Residual Vectors to enhance the frequency domain and to get a better result.

Modal solution combines multiple modal responses to replicate the deformations of your structure, so if you cut the lower frequencies/modes you will lose accuracy.

the basic idea follows fourier series principle, where a generic function can be decomposed into sine/cosine functions. If you remove some frequencies, you lose accuracy.