Created attachment 180768 [details]
File used in the unit test.

The test below should fail in "save" but it does not.

Problem is, that the validator produces for the double attribute not a string with "Error", but a string with "Fatal".
So line
    if( aContentOUString.indexOf("Error") != -1 )
[https://opengrok.libreoffice.org/xref/core/test/source/bootstrapfixture.cxx?r=5200a736#239]
does not catch the failure.

I guess the line should be
    if (aContentOUString.indexOf("Error") != -1 || aContentOUString.indexOf("Fatal") != -1)
With that change the test fails as expected. But I don't know whether such change will produce problems somewhere else.

For reproducing the problem, the following unit test has to be added to file core/xmloff/qa/unit/draw.cxx and the attached file to core/xmloff/qa/unit/data

CPPUNIT_TEST_FIXTURE(XmloffDrawTest, testTextRotationPlusPre)
{
    // import
    getComponent() = loadFromDesktop(m_directories.getURLFromSrc(DATA_DIRECTORY)
                                         + "tdf149551_verticalText.pptx",
                                     "com.sun.star.presentation.PresentationDocument");
    // The file has a shape with attribute vert="vert" in <bodyPr> element. That generates a
    // TextPreRotateAngle attribute in CustomShapeGeometry.

    // Add a TextRotateAngle attribute.
    uno::Reference<drawing::XShape> xShape(getShape(0));
    uno::Reference<beans::XPropertySet> xShapeProps(xShape, uno::UNO_QUERY);
    uno::Sequence<beans::PropertyValue> aGeomSeq;
    xShapeProps->getPropertyValue("CustomShapeGeometry") >>= aGeomSeq;
    auto aGeomVec(comphelper::sequenceToContainer< std::vector<beans::PropertyValue> >(aGeomSeq));
    aGeomVec.push_back(comphelper::makePropertyValue("TextRotateAngle", sal_Int32(45)));
    aGeomSeq = comphelper::containerToSequence(aGeomVec);
    xShapeProps->setPropertyValue("CustomShapeGeometry", uno::Any(aGeomSeq));

    // Save to ODF. Without the fix, a file format error was produced, because attribute
    // draw:text-rotate-angle was written twice, one from TextPreRotateAngle and the other from
    // TextRotateAngle.
    utl::TempFile aTempFile;
    save("impress8", aTempFile);
}