I restested this scenario with a multifile torrent of around 10 GB, with files usually around 350 MB.

The integrity check after the creation was OK.

The single file scenario, I tested that when I fixed this bug, I used a 4.6 GB tar file, that also was OK.

Could you verify your 8 GB torrent with azureus ? If AZ finds all chunks OK, then we know that the problem is with the integrity check. If it is not OK, then it must be with the creation of the torrent.