In summary, our investigations give insights into the errors in the vibrational frequencies and associated IR and Raman intensities when using the PHVA approximation both for full QM and QM/MM approaches. Notably, the errors were more pronounced in the low-frequency part of the spectrum, but they can also be substantial in the higher-frequency parts. Additionally, we show how to identify normal modes with high pseudo-translational and pseudo-rotational contributions so that they can be removed since they are poorly described within the PHVA approximations. Lastly, with regard to the QM/MM scheme, our work shows that hydrogen-bonded solvent molecules should be included in the QM subsystem to avoid very large errors. In particular, when there are hydrogen-bond donors in the QM subsystem.