Attach multiple files in PDF using Aspose.PDF for .NET - System.AggregateException occurs

I am using aspose.pdf 19.12. While creating a pdf with multiple fileattachmentannotations, it’s working up to 2 or 3 attachments but failing with more than that.
Following is the exception I am getting.

System.AggregateException: One or more errors occurred. (Object reference not set to an instance of an object.) —> System.NullReferenceException: Object reference not set to an instance of an object.
at #=zvX2yIBsTw4G1HZ2w$AAaF1Q=.#=zn1BeGyU=()
at Aspose.Pdf.Cell.#=zGFvI1JvqLRyt(Table #=znRxZkSs=, Double #=zWKu$NsE=, Page #=zAd34nB8=, Double #=zbYmfYU4=, Double #=z9_gFxB8=, Boolean #=zF0XKWxssEYo7g$jppQbVaC0=)
at Aspose.Pdf.Row.#=z2D4tBk0UBYWfWPvDWw==(Table #=znRxZkSs=, Page #=zAd34nB8=, Double #=z9_gFxB8=, Double #=zbYmfYU4=, Int32 #=z2Tvrmrk=)
at Aspose.Pdf.Row.#=zn1BeGyU=(Table #=znRxZkSs=, Double& #=z9_gFxB8=, Double& #=zn5rVsA4=, Boolean #=zEplkWrzoex3P, Double #=zYpYXatXBU3QY, Double #=zbYmfYU4=, Page #=zAd34nB8=, Int32& #=z_vDHN_FjMVZo)
at Aspose.Pdf.Table.#=zn1BeGyU=(Double& #=zn5rVsA4=, Double& #=z9_gFxB8=, Boolean #=zEplkWrzoex3P, Double #=zGmAxT7k2Bh7v, Double #=zbYmfYU4=, Page #=zAd34nB8=, Boolean #=zbHeMzgjjic8H, List1 #=zAN7vVbA=) at #=zvX2yIBsTw4G1HZ2w$AAaF1Q=.#=zn1BeGyU=() at Aspose.Pdf.Cell.#=zGFvI1JvqLRyt(Table #=znRxZkSs=, Double #=zWKu$NsE=, Page #=zAd34nB8=, Double #=zbYmfYU4=, Double #=z9_gFxB8=, Boolean #=zF0XKWxssEYo7g$jppQbVaC0=) at Aspose.Pdf.Row.#=z2D4tBk0UBYWfWPvDWw==(Table #=znRxZkSs=, Page #=zAd34nB8=, Double #=z9_gFxB8=, Double #=zbYmfYU4=, Int32 #=z2Tvrmrk=) at Aspose.Pdf.Row.#=zn1BeGyU=(Table #=znRxZkSs=, Double& #=z9_gFxB8=, Double& #=zn5rVsA4=, Boolean #=zEplkWrzoex3P, Double #=zYpYXatXBU3QY, Double #=zbYmfYU4=, Page #=zAd34nB8=, Int32& #=z_vDHN_FjMVZo) at Aspose.Pdf.Table.#=zn1BeGyU=(Double& #=zn5rVsA4=, Double& #=z9_gFxB8=, Boolean #=zEplkWrzoex3P, Double #=zGmAxT7k2Bh7v, Double #=zbYmfYU4=, Page #=zAd34nB8=, Boolean #=zbHeMzgjjic8H, List1 #=zAN7vVbA=)
at #=zvX2yIBsTw4G1HZ2w$AAaF1Q=.#=zn1BeGyU=()
at Aspose.Pdf.Page.#=zX9_L5Mk=(Page #=zAd34nB8=)
at Aspose.Pdf.Page.#=zgilXBdvBVzI6vOHIjA==()
at Aspose.Pdf.Document.ProcessParagraphs()
at Aspose.Pdf.Document.#=zdgGX2$gBqT6z(Stream #=zS1bs0l8=, SaveOptions #=zv8U117SYibvt)
at Aspose.Pdf.Document.#=zVF35lWfacBPN(Stream #=zq5lg74c1aj55, SaveOptions #=zGW_1OEU=)
at Aspose.Pdf.Document.Save(Stream outputStream, SaveFormat format)

@hrd.saha86,

Can you please share source files along with sample code so that we may further investigate to help you out. Before sharing requested information can you please try to use Aspose.PDF latest version 20.1 on your end and share feedback with us.