Hi Richard,
It might be worth checking the top batten adjuster?
There is a good picture of one on the RS Parts Store Here:-
pastinghttps://www.rssailingstore.com/Catalogue/Sails-Covers/RS-Aero/RS-Aero-RS-Neo-Batten-Adjuster-AER-SA-903
It is worth enlarging the image.
When you look at the adjuster in the sail you should see the two wings engaged in the webbing loops and the small 'bubble' of plastic in the centre of the body between the wings.
If you don't see the 'bubble' then chances are the adjuster is the wrong way round and needs to be flipped over.
When inserted correctly, from the port side of the sail, the wings are offset toward the sail, i.e. to starboard. And there is no bubble on the opposite side; the side that normally bears against the sail.
I don't know for sure because I've never had this happen to me, but I can imagine the top batten having an opposite bias, to starboard tack, if the adjuster is inserted 'flipped over'.
Regards, Jonathan