Try changing the point on the clew where the sheet connects. This will affect the amount of twist in the sail. It sounds like you have too much twist. Assuming you have a clew plate on the jib with multiple holes for connecting the sheet, I would attach the sheet to one of the holes higher up on the jib to put more sheeting force toward the top of the sail to reduce twist.
yes, too much twist. Apart form changing the clew, less mast rake could be an option too.
Cheers,
Klaus
