I believe in many of the 20-30 year old piston twins I fly, friction nuts can be notoriously unreliable.
I have to date had two take-offs extended unintentionally, due to faulty friction nuts, it will not happen again, to me anyway.
Power reductions due to a combination of no hand on throttle and faulty or incorrectly adjusted friction nuts are very difficult to determine by ear and often occur at a point after performance figures may have already been checked.
Obviously, if the boss decides to get that new GV I won't be bothered by such third world problems
Willie