Rudder tramping occurs with full rudder application (as needed when engine fails at low speed) on several types that come to mind - F27 being the most notable. I am unsure what is the cause. Could be due to play in the trim tab circuit, could be prop wash, could be the rudder or trim tab at point of stall. Probably varies with type. Any ideas?
The thought of rudder lockout is a whole lot more scary. Never experienced that one. But then I never attempted to sideslip a DC3 and can't imagine any reason why anyone would. The whole hinge setup at the back end of a DC3 looks too flimsy to be messing with radical moves.