The vacuum infusion process is a Liquid Composite Manufacturing (LCM) process in which the preformed reinforcing fibres are impregnated with the fluid matrix using the pressure difference produced by the evacuation of the mould cavity. In order to speed up the infiltration process, it is common to use a highly permeable flow distribution medium on top of the preform. On doing so, thw matrix infiltrates the preform predominantly through the thickness direction of the part. Filling simulations of such vacuum infusion processes having layers with vastly different permeabilities, when done with software tools that make use of the Finite Volume Method (FVM) typically show an incomplete filling of the bottommost layer of cells, which is in contrast to what is observed experimentally. This work aims to study this error and propose solutions for rectifying this error.