Sounds to me like as the piston is lifting the needle up its kicking ever so slightly sideways & loading up the needle & eventually causing it to snap.
Check how much movement is in the piston as either the bore or piston itself is probably worn.
Said by a very brave soul " Lets Roll & Remember To Burn Rubber Not Your Soul "
Words of wisdom
Give big space to the festive dog that makes sport in roadway. Avoid entanglement of dog with wheel spokes.
Go soothingly on the grease mud, As there lurks the skid demon. Press the brake foot as you roll around the corners, And save the collapse and tie up.
F650GS Dakar in Australia