strange BRepAlgoAPI_Fuse behavior

Hello,

I have two quite complex shapes resulting from a serie of operations over primitives. Both shapes are valid according to the BRepCheck_Analyzer:

BRep_Builder builder;

TopoDS_Shape shape1;
BRepTools::Read(shape1, "shape1.brep", builder);
BRepCheck_Analyzer analyzer1(shape1);
cout

TopoDS_Shape shape2;
BRepTools::Read(shape2, "shape2.brep", builder);
BRepCheck_Analyzer analyzer2(shape2);
cout

TopoDS_Shape fuse = BRepAlgoAPI_Fuse(shape1, shape2);
BRepCheck_Analyzer analyzer3(fuse);
cout

When I try to merge them using BRepAlgoAPI_Fuse() I receive an unexpected result (see attached picture). You can see there is a face missing between the selected edges of the shape1. According to the BRepCheck_Analyzer even the resulting fuse shape is valid.

Any subsequent BRepAlgoAPI_Fuse() operations on the fuse shape finally leads to the Standard_ConstructionError being thrown.

Can anything else be wrong with the source shapes shape1 and shape2 even the BRepCheck_Analyzer reports them as valid?

Or is it a bug of the BRepAlgoAPI_Fuse()?

Or something else what I am missing there?