Non converging Fmax in energy minimization

Interesting. What you are showing is that the EM procedure did not achieve its goal (Fmax < 1000), but that doesn’t mean necessarily that it failed (i.e. crashed).

Do try some of the fixes that some other users pointed out in this post

You can also try to minimize individually the ligand and the APO protein, only for the sake of checking that their individual geometries are not problematic.