Today I put on the Berkley Vanish Fluorocarbon 12lb test fishing line on my Quantum Smoke baitcasting reel. I thought i had made a great choice, but on my first cast i kept my thumb on the line, but still saw some mild backlash, i pulled some line out and noticed that the more i pulled out, the worse the backlash and loose line got. I pulled all of it out to the knot, then reeled it back in. My next cast, I was extra carefull to tightly keep my thumb on the line, but it did the same thing. I pulled all of it out and cut the line. Can someone tell me why this happened?