transparent page have black lines

[Suddenly-TurnRound]

I changed the background color of the report page to transparent and added white background with borderless text on the page. After exporting to PDF, black lines appear in the PDF file. What should I do

FastReport.OpenSource.Export.PdfSimple, .NET

code:
List list = new List();
report.Prepare();
using (MemoryStream reportImageStream = new MemoryStream())
{
using PDFSimpleExport pdf = new PDFSimpleExport();
pdf.PageRange = FastReport.PageRange.All;
report.Export(pdf, reportImageStream);
list.Add(Convert.ToBase64String(reportImageStream.ToArray()));
}
return list;

文件.zip