If you get a piston extending/retracting as fast as is possible before the piston is receiving pulses so fast it just stays extended, it appears to cause something like the Piston Translocation Bug. It pulls you toward the piston, and you are stuck there in an inescapable loop until you break one of the observers.
World download attached as .zip. The device in question is surrounded by Redstone torches and has a cobblestone Piller with Redstone torches all over it nearby. NOTE: Place blocks under the piston head, otherwise gravity is stronger than the piston.