PDF/A validation fails

Hi.

We use your product for pdf/a files generation.
Some files have validation issues. For example if we convert html to pdf/a we may have such issues:

Validating file "test.html.pdf" for conformance level pdfa-1b
The value of the key N is 4 but must be 3.
A device-specific color space (DeviceRGB) without an appropriate output intent is used.
The document does not conform to the requested standard.
The document doesn't conform to the PDF reference (missing required entries, wrong value types, etc.).
The document contains device-specific color spaces.

PDF-Tools PDF validator is used for validating (http://www.pdf-tools.com/pdf/validate-pdfa-online.aspx).

We use rather simple code for conversion:

var license = new Aspose.Pdf.License();
license.SetLicense("Aspose.Total.lic");

Aspose.Pdf.Document pdf = new Document(inputFilePath, new HtmlLoadOptions());

pdf.Convert(new MemoryStream(), Aspose.Pdf.PdfFormat.PDF_A_1B, Aspose.Pdf.ConvertErrorAction.Delete);

pdf.Save(outputFilePath);

PS. XLS, TXT, EMF, WMF files also converted to pdf/a with validation issues.