well, after seeing pics of the Mk4 cap, i think i can see why the lanyward twists on the MK5.
on the mk5, the lanyard is mounted right next to filler cap (directly onto the body of the car). on the MK4, it is mounted on the hinge of the flap. So, on the MK5, the lanyard is stretched out and under tension more when you are trying to sit the cap on the flap. On the Mk4, the lanyard has more slack so even though it is twisted, it is far less noticeable and has less effect on the cap not resting properly on the flap.
In essence, the lanyard is too short.
The only decent solution is to find a way of extending the lanyward... or finding another model in the VAG range that has the longer lanyard..
Rich