the symbols xschem uses for saving nodes work only at the top level, HSPICE recognized also '.probe node ...' statements inside .SUBCKTs so only those specified internal variables where saved. ngspice does not handle .probe inside subckts, so these need to be flattened to the top: instead of a .probe node inside a x1 subckt you need a '.probe v(x1.node)' at the top...