2 models with exactly the same input except modal analysis cutt off frequency is different, why are the first set of mode shapes NOT exactly the same?
Changing the cut-off frequency when automatic mass points option is enabled will lead to different level of discretization in the model. That should explain the differences in the frequencies. The results should not be the same as the input between the two models are no longer "equivalent" - because the level of discretization is not same. Higher the cutoff frequency, would be a higher level of discretization.
"Mode Shape" sub report
Bentley AutoPIPE