Contacted Plextor, their reply is as follows.
The effect you reported is not related to the software or the converter itself but to
the structure of the old analogue videos. Due to the construction of a video camera
or a vhs video recorder the signals meant for vertical and horizontal synchronising
lead to a perfect result on the tv screen. If there is a slight mis-synchronizing
either in the vertical or horizontal area of the picture-signal itself it remains invisible
on the tv screen due to the tv standard. But this becomes visible in case you record this
file onto your harddisk and try to play it back either on a tv screen or on your computer
The converter and software you are using are running perfectly fine.
You might want to edit the files you recorded with a video editor.
Is there an editor that can remove this band or correct the problem?