The check wheter the mous is inside the tree is faulty.

Here's the patch to make it work, around line 11650 in TeeTree.pas


  // Returns True if mouse is inside any shape or shape "cross-box"...
  Function CheckMouseShapes:Boolean;
....
        if NeedsHint then
        begin
          P:=Canvas.Calculate3DPosition(X1,Y1,TeeTreeZ);
{$ifdef HH_PATCH_MOUSEMOVE_NEEDSHINT}
          NeedsHint:=ChartBounds.Contains(P);
{$else}
          NeedsHint:=(P.X>ChartBounds.Right) or (P.Y>ChartBounds.Bottom);
{$endif}

          if not NeedsHint then
          begin
            P:=Canvas.Calculate3DPosition(X0,Y0,TeeTreeZ);
{$ifdef HH_PATCH_MOUSEMOVE_NEEDSHINT}
            NeedsHint:=ChartBounds.Contains(P);
{$else}
            NeedsHint:=(P.X<ChartBounds.Left) or (P.Y<ChartBounds.Top);
{$endif}
          end;
        end;
....