Sometimes if the prey item gets too cold they won't consume it. Maybe try to offer the F/Ts a little bit hotter so they maintain their temperature after he coils it. I just had this happen yesterday with one of our Volta hatchlings, she striked, coiled, and then dunked the rodent in the water before putting it on the paper towels. This cooled the F/T down too far and she just wasnt interested afterwards.