In this work, we present the newly developed MRS fitting software ProFit-v3, including adaptive baseline stiffness control and a newly proposed cost function calculation. ProFit-v3 was evaluated for accuracy and precision using both simulated and in vivo spectra, and the results were compared against LCModel. The adaptive spline baseline model of ProFit-v3 modelled different simulated baseline distortions well. The fitting accuracy measured on simulated data was slightly better for ProFit-v3 than for LCModel. While the fitting precision of ProFit-v3 was comparable to that of LCModel for the simulated data, LCModel proved to be somewhat more precise for in vivo spectra.