Indeed Simon,I had a similar problem with the Girdraulics on my Shadow and it was the top link FF4 which had been machined wrong. End faces of the area where the flanged bronze bush FF6 press in were not machined equally central through the axis in relation to where the link attached to the head clip FF1 thus it tried to throw the fork leg sideways at the top. The top link FF4 was not bent or distorted in any way, just machined wrong which was clear when placing another good link on top of the problem one. To correct it I ended up machining new FF6 bush with different thickness flanges which resulted in the forks all aligning up. It took days to realise what was going on and yes the bike had being run with this error for years by the previous owner and probably like that from new.
Probably something similar in some of the bushes or link happening with mine..