I was thinking a bit more about this - I think it is that Piper has actually worked out how to do the "tickle-sucking" that is what is needed to stimulate another letdown. Which in principle is excellent progress!
You need to relax physically as much as you can - breathe deeply, try and let your shoulders droop. That way the letdown will come sooner, and the tickling will stop.
You will probably get less sensitive to it pretty quickly.