Planetary masses are crucial quantities in the field of exoplanet studies. Mass determines whether an object can be classified as a planet, it guides the analysis of the dynamics of planetary systems, and it models our prior information about the physical and chemical properties of exoplanets, from the interior composition to atmospheric features. The fundamental method in mass determination is the analysis of the Radial Velocity (RV) curves of the host stars, the so-called RV method. Although the RV method has been extensively used in the last two decades, it relies heavily on the application of Markov Chain Monte Carlo (MCMC) algorithms to fit the Keplerian Model (KM) to RV data. We show how an intrinsic degeneracy in the time and shape parameters of the KM influences the robustness and thus the reliability of the outcomes as best fit values for every parameter of the model and in particularly for the value of the RV semi-amplitude.