cdrskin: formatting blank=format_defectmgt: % is jumpy (DVD-RAM)

[Giulio <giulioo@gmail.com>]

cdrskin-1.1.8

Linux RHEL5 in a VMware VM, using host's SATA burner
cdrskin: Overview of accessible drives (1 found) :
-----------------------------------------------------------------------------
0  dev='/dev/sr0'  rwrw-- :  'HL-DT-ST'  'DVD+-RW GH50N'

I format a DVD-RAM with
	cdrskin --allow_setuid dev=$cddev -v blank=format_defectmgt

formatting finishes ok (about 1 hour), however the % shown during the
formatting is not correct, it looks something like
	1%   78%   40%  ..  2%   22%   98%    ...   3% .... 100%
that is, every now and then you can see a number that is the actual %, but
it alternates with random % numbers.

If I use
	dvd+rw-format -force=full /dev/cdrom
the % increases monotonically (1% ... 3% ... 50 % ..... 100%)