LibDock problem

This must be quite trivial but I have not found the right way to do it. I am using LibDock (DS2020) to dock a collection of ligands into a receptor. I am finding that if I perform the regular docking with default parameters and without any minimization after docking, the calculation finishes and I get docked poses for every ligand. However, if I run LibDock selecting any of the available postdocking Minimization Algorithms that appear on the menu, then the calculation finishes raising an error and does not provide any result because it fails to minimize all of the docked ligands. I have also tried to minimize some of those using the In situ Ligand Minimization option, but with the same result. I do not understand what is wrong with this and DS2020 does not seem to provide any additional info that can drive me to fix the problem. Any help would be appreciated.