If you depower the kite fully, so rearlines are slack - does it still pull "heavily" to one side then ?
If not, simply move the rearlines till it flies straight, with bar pulled - and see how it behaves then.
If it turns okay to both sides now, you should just make a pigtail a bit shorter, and everything is sorted out
If it turns a lot to one side, even with slack rearlines, the kite is most likely defect beyond reasonable "fixability", and you have to send it back
You should be able to see if the front bladder is twisted a lot, if pumped up on a windless day, but if it is a onepump kite (like almost all are today), it can not be twisted so much that it will matter IMO, because the vents will hold it in place.
It was only on the old kites a twisted LE bladder could occur and make the kite "wrong"