The bladder should not have popped inside the leading edge, shouldnt think it was a twist, more likely as you said it tore along the seam, there was probably some of the seam stitching broken that you had not noticed. Would only need a few bad stitches, then once pumped up and under high pressure the bladder would force its way out the small hole making it bigger and then blow out.
You will need to get the leading edge repaired properly with stitching, kitefix or other tape will not hold it strong enough.
Kite repairs south east UK near London