this is rare case that happen to me.
the proper way to exit B line stall was to let B riser up slowly..
thats how I did many times without problem eventhough the wind quite strong..
last time.. in Maninjau, I exp this.. the wing surge forward eventhough I let it go slowly..then I counter it with a little brake.. then guess what? my wing spin . Luckily Im just hands up.. then it return back to normal.
I guess the wing surge forward when it enter the thermal and by time I encounter it.. Im inside the thermal already..may be that coz the spin..
advice from Nasa- let the wing pick up the speed after exiting B line stall.