I use to have line twist all the time. I didn't jump for 3 months in the winter ( i'm a sisi what can i say) and when i started jumping again I made a demo full ( just to be sure...) and i discovered i was unstable during opening. I've realized that i put my left hand to close to my head = a soft spin on opening = a line twist. After I've fixed this i get on heading opening all the time.