error in calculating the shape volume

Dear Dmitrii,

I'm afraid I cannot provide you the model file, as the model in question was built out of a filed model.

The reason of rebuilding it myself is that I want a closed shape (which is more suitable for volume calculation) and the code is here:
=================================================================
BRepBuilderAPI_Sewing sewing;
sewing.SetTolerance(1e-3);
sewing.Add(shape);
sewing.Perform();
TopoDS_Shape sewedShape = sewing.SewedShape();

BRepBuilderAPI_MakeSolid makeSolid;
for (TopExp_Explorer ex(sewedShape, TopAbs_SHELL); ex.More(); ex.Next()) {
TopoDS_Shell shell = TopoDS::Shell(ex.Current());
makeSolid.Add(shell);
}

if (!makeSolid.IsDone()) {
// Failed to make a solid
std::cout << "Failed to make a solid." << std::endl;
return false;
}

TopoDS_Shape m_shape = makeSolid.Shape();
=================================================================

So when I used m_shape for volume calculation, I got a minus value.

Dear Dmitrii,

Something relevant to add here.

I also tried to write the m_shape to a .STP file and then read the m_shape again from the file.
To my surprise, this time the newly-loaded m_shape yielded a positive value, with the same absolute value as the minus one.

This could be a workaround but it's unacceptable, as the writing and the re-loading is very time-consuming.

Is it possible to figure out what's wrong with my building the shape?

Thanks.

Dear Dmitrii,

Thank you very much.

The version of OCCT is OpenCASCADE-7.7.0-vc14-64.

And I also attached the original model file for your reference, which is an IGS file.