After merge nested bookmarks are duplicated

Hello to everyone at the support team,

im trying to merge some PDF files with nested bookmarks. The goal is to preserve the existing bookmark structure after the merge.

1. Merge two pdf files s1.pdf and s2.pdf to result.pdf
2. Create new bookmark for document  s1.pdf and read existing bookmarks from s1.pdf and assign them as child bookmarks
3. Create new bookmark for document  s2.pdf and read existing bookmarks from s2.pdf and assign them as child bookmarks
4. Save bookmarks

For more details see the attached test project.

Aspose.Pddf.dll Version 9.0.0.0
internal bugid#4414

In the result.pdf all nested bookmarks are duplicated. Very strange.

Best regards, Martin Pfeifer