BRepOffsetAPI_ThruSections reverses direction of (half of) wires

Hi, 

I'm having some issues creating a 'ThruSections' Loft.

I created 40 wires representing crossections of a donut-like shape, 

using a translation and rotation on an initial wire, the wires are placed properly,

but when I build the shape using BRepOffsetAPI_ThruSections, the wires seem to reverse direction once they cross the xz-plane (after the 20th wire), see:

http://www.jvanderspek.com/pub/profile_flip.png

the code is as follows:

pnts = []
pnts.append( gp_Pnt( w2, 0, 0) )
pnts.append( gp_Pnt( w2 - b, 0, h2) )
pnts.append( gp_Pnt( w2, 0, h) )
pnts.append( gp_Pnt( -w2, 0, h) )
pnts.append( gp_Pnt(-w2 + b, 0, h2) )
pnts.append( gp_Pnt( -w2, 0, 0) )

segs = []
segs.append( GC_MakeArcOfCircle(pnts[ 0 ], pnts[ 1 ], pnts[ 2 ]) )
segs.append( GC_MakeSegment(pnts[ 2 ], pnts[ 3 ]) )
segs.append( GC_MakeArcOfCircle(pnts[ 3 ], pnts[ 4 ], pnts[ 5 ]) )
segs.append( GC_MakeSegment(pnts[ 5 ], pnts[ 0 ]) )

wire = BRepBuilderAPI_MakeWire()
for i in range( 0, len( segs ) ):
    edge = BRepBuilderAPI_MakeEdge( segs[ i ].Value() )
    wire.Add( edge.Edge() )

wires = []
for i in range( 0, n ):
    trn = gp_Trsf()
    trn.SetTranslation( gp_Vec( w, 0, 0 ) )
    wt = BRepBuilderAPI_Transform( wire.Wire(), trn )
    trn = gp_Trsf()
    trn.SetRotation( gp_Ax1( gp_Pnt( 0, 0, 0 ), gp_Dir( 0, 0, 1 ) ), ( i / n ) * 2 * math.pi )
    wires.append( BRepBuilderAPI_Transform( wt.Shape(), trn ) )

loft = BRepOffsetAPI_ThruSections( False, False )
loft.SetSmoothing( False )
loft.SetContinuity( GeomAbs_G2 )

for i in range( 0, len( wires ) ):
    loft.AddWire( topods.Wire( wires[ i ].Shape() ) )

could anyone shed some light as to what's happening here ?

thanks,

Jonathan