Are the eggs room temperature to begin with? That seems important to me... Otherwise perhaps vary the duration. I've had great success with this method but YMMV.
I don't see how any modulation of the timing can produce anything other than a thicker or thinner layer of white stuck to the inside of the shell. What exactly happens when you do it - does all the white come out? Do you use older eggs perhaps? The older the egg, the less the shell sticks - but the more it disintegrates in water, so I always try and use fresh ones or poaching...