PDFTK breaks bookmark urls while merging files

I have a pdf file with attached bookmarks. When I try to merge another pdf files pdftk breaks boomarks (they are still present but when I click on them nothing happens)

pdftk aio_single.pdf another.pdf output aio.pdf

I am using pdftk 2.02a version

I have noticed that pdftk generates invalid BookmarkPageNumber, but don't know why :/

BookmarkBegin
BookmarkTitle: Table of Contents
BookmarkLevel: 1
BookmarkPageNumber: 0
BookmarkBegin
BookmarkTitle: Daily Drilling Reports
BookmarkLevel: 1
BookmarkPageNumber: 0
BookmarkBegin
BookmarkTitle: 103/09-31-049-11W5/00
BookmarkLevel: 2
BookmarkPageNumber: 0
BookmarkBegin
BookmarkTitle: Date: 2019-03-11
BookmarkLevel: 3
BookmarkPageNumber: 0
BookmarkBegin
BookmarkTitle: DAILY SUMMARY
BookmarkLevel: 4
BookmarkPageNumber: 0