We address the question of why so far most of the simulation approaches to find the energy of vanishing flow (EVF) in light systems have failed to reproduce the experimental data. By investigating systematically the dependence of the EVF on the initial setup of the nuclei in these approaches we find out that for light systems a small variation of this setup can create large differences in the EVF whereas for large systems the dependence is weak. These studies have been done with the isospin-dependent quantum molecular dynamics model.