Piston Extending and retracting onto another piston dupes the other piston.

Sticky piston on 4 tick - delay using a repeater, extending onto the backside of another sticky piston (Horizontally, on the ground) and then retracting, will sometimes not retract the sticky piston in front of it, but instead seem to retract a piston that does not exist, out of said piston. Thus creating/duplicating the sticky piston.