Created attachment 617 [details]
The unpatched result (nitice yellow series drawon over green seirs, making values of green series impossible to analyse

Created attachment 618 [details]
Patch installed. crossing x axis still ugly but at leas values are displayed correctly

Patches applied to series.pas (using condition compiling for HH_PATCH_TC_STACKEDAREA)

interface
....
  TCustomSeries=class(TCustomLineSeries)
....
    Function PointOrigin(ValueIndex:Integer; SumAll:Boolean):Double;  {$ifdef HH_PATCH_TC_STACKEDAREA} virtual; {$endif}
....


  TAreaSeries=Class(TCustomSeries)
....
{$IFDEF HH_PATCH_TC_STACKEDAREA}
    Function PointOrigin(ValueIndex:Integer; SumAll:Boolean):Double; override;
{$ENDIF}  public
....

implementation

....

{$ifdef HH_PATCH_TC_STACKEDAREA}
// negative values are wrongly stacked in the original code. This overriden
// function calculates the correct origin value for each datapoint
Function TAreaSeries.PointOrigin(ValueIndex:Integer; SumAll:Boolean):Double;

   Function LocalPointOrigin:Double;
   var t         : Longint;
       tmpSeries : TChartSeries;
       val:double;
       sumneg,sumpos:boolean;
   Begin
     result:=0;
     // first of determine wheter we have to sum negative or positive values
     val:=MandatoryValueList[ValueIndex];
     sumneg:=val<0;
     sumpos:=val>=0;

     if Assigned(ParentChart) then with ParentChart do
     begin
       if SumPos then
       begin
         for t:=0 to SeriesList.Count-1 do
         Begin
           tmpSeries:=Series[t];
           if (not SumAll) and (tmpSeries=Self) then
             Break
           else
           With tmpSeries do
           if Active and SameClass(Self) and (tmpSeries.Count>ValueIndex) then
           begin
             val:=GetOriginValue(ValueIndex);
             if (val>=0.0) and sumpos then
               result:=result+val
           end;
         end
       end
       else if SumNeg then
       begin
         for t:=0 to SeriesList.Count-1 do
         Begin
           tmpSeries:=Series[t];
           if (not SumAll) and (tmpSeries=Self) then
             Break
           else
           With tmpSeries do
           if Active and SameClass(Self) and (tmpSeries.Count>ValueIndex) then
           begin
             val:=GetOriginValue(ValueIndex);
             if (val<0.0) then
               result:=result+val
           end;
         end;
       end
     end;
   end;

Begin
  if MultiArea in [maStacked,maStacked100] then
    result:=LocalPointOrigin
  else result:=inherited PointOrigin(ValueIndex,SumAll);
End;
{$ENDIF}