I'm gonna go out on a limb here........if memory serves, that unit has 1 or 2 arms on it. If that is so, and you are using your regular decoys, this is what I'm thinking. Regular dekes are nearly neutral bouyancy.....they sink very slowly. The fins on them are intended to propel the decoy forward as it descends. If you hooked your decoy up as usual, I would think the decoy would want to "ride"........make that be drug, through the water with its nose at a rather steep angle......like a helicopter does when it want to go forward quickly. This would put so much drag on it, the spinner would go too fast and end up twisting the line, like you noticed.
My suggestions would be to some how attach you line much closer to the nose, or use a decoy that is much more tail heavy and with minimal fins......just enough to make it "swim" nose first.
I hope this makes sense......it just seems that a decoy made to glide, without being towed, but rather as it descends on its own, just wouldn't have the same hydrodynamics as one being drug around by a line attached to its back........just my $.02