dvdunauthor, unexpected exit

I just launched dvdunauthor on a video dvd but it seems it stopped too early and it didn't create 
the file `dvdauthor.xml'. Here's its output:

$ dvdunauthor /media/ROADTOPERDITION_PAL_ITALY
DVDAuthor::dvdunauthor, version 0.6.18+.
Build options: gnugetopt imagemagick iconv freetype fontconfig
Send bug reports to <dvdauthor-users-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>

libdvdread: Using libdvdcss version 1.2.10 for DVD access
libdvdread: Attempting to use device /dev/sr0 mounted on /media/ROADTOPERDITION_PAL_ITALY for CSS 
authentication


INFO: VMGM

libdvdread: Attempting to retrieve all CSS keys
libdvdread: This can take a _long_ time, please be patient

libdvdread: Get key for /VIDEO_TS/VIDEO_TS.VOB at 0x00000143
libdvdread: Elapsed time 0
libdvdread: Get key for /VIDEO_TS/VTS_01_0.VOB at 0x00000216
libdvdread: Elapsed time 0
libdvdread: Get key for /VIDEO_TS/VTS_01_1.VOB at 0x00000c28
libdvdread: Elapsed time 0
libdvdread: Get key for /VIDEO_TS/VTS_02_0.VOB at 0x0025863b
libdvdread: Elapsed time 0
libdvdread: Get key for /VIDEO_TS/VTS_02_1.VOB at 0x00258659
libdvdread: Elapsed time 0
libdvdread: Get key for /VIDEO_TS/VTS_03_0.VOB at 0x0025b2ec
libdvdread: Elapsed time 0
libdvdread: Get key for /VIDEO_TS/VTS_03_1.VOB at 0x0025b30a
libdvdread: Elapsed time 0
libdvdread: Get key for /VIDEO_TS/VTS_04_0.VOB at 0x0025b322
libdvdread: Elapsed time 0
libdvdread: Get key for /VIDEO_TS/VTS_04_1.VOB at 0x0025b340
libdvdread: Elapsed time 0
libdvdread: Get key for /VIDEO_TS/VTS_05_1.VOB at 0x00265322
libdvdread: Elapsed time 0
libdvdread: Get key for /VIDEO_TS/VTS_06_1.VOB at 0x00265348
libdvdread: Elapsed time 0
libdvdread: Get key for /VIDEO_TS/VTS_07_1.VOB at 0x0026536e
libdvdread: Elapsed time 0
libdvdread: Get key for /VIDEO_TS/VTS_08_1.VOB at 0x00265394
libdvdread: Elapsed time 0
libdvdread: Get key for /VIDEO_TS/VTS_09_1.VOB at 0x002653ba
libdvdread: Elapsed time 0
libdvdread: Get key for /VIDEO_TS/VTS_10_1.VOB at 0x002653e0
libdvdread: Elapsed time 0
libdvdread: Found 10 VTS's
libdvdread: Elapsed time 0
STAT: [1] VOB 2, Cell 1 (18%)

INFO: VTSM 1/10
STAT: [4] VOB 3, Cell 3 (18%)
ERR:  Error 17 reading data: File exists
STAT: [22] VOB 11, Cell 2 (91%)

INFO: VTS 1/10
STAT: [39] VOB 2, Cell 14 (100%, 0:00 remain)

INFO: VTSM 2/10
STAT: [4] VOB 1, Cell 5 (80%)

INFO: VTS 2/10
STAT: [1] VOB 2, Cell 1 (100%, 0:00 remain)

INFO: VTSM 3/10
STAT: [4] VOB 1, Cell 5 (80%)

INFO: VTS 3/10
STAT: [0] VOB 1, Cell 1 (0%)

INFO: VTSM 4/10
STAT: [4] VOB 1, Cell 5 (80%)

INFO: VTS 4/10
STAT: [1] VOB 2, Cell 1 (100%, 0:00 remain)

INFO: VTSM 5/10
$

It seems libdvdread detected 10 titlesets, didn't it?
But the process copied just 5 titlesets and no dvdauthor.xml was created, why?

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