Playing Sword of Berserk NTSC/J on Australian Ver. of DC

I have this game and the whole thing works fine, except that
some specific FMV (movies) doesn't run smoothly.
The picture stops and go and also the sound does not flow.
Does anyone know what the problem is? I tried it on the Japanese
version of Dreamcast and it worked fine. But when I try it
on my Australian DC, it does that.
Is it the difference between the Aus and Jap version of DC lens?
or the motor.
It's not much of a problem, but I am just too curious why it does
that on Aus Version of DC.
Please help..!!