When you tie the knotless knot come back down the barrel of the knot a few times before putting the tag back through the eye of the hook. This helps to stop the material from contracting during the fight and snapping and should hopefully solve your problem.
Also 12lb in a fluorocarbon isn't very strong and as its invisible anyway I would look at a higher/thicker breaking strain.
Back to basics again today, free lining dog biscuits for three more chub, 2lb ish (which I didn't weigh), 3lb2oz, and 4lb2oz.
I got stung to pieces, and wet feet, but when they look like this the biggest, who cares?
Just noticed my unhooking mat,