Autorotation is one.
Strong Crosswinds at hover is another.
Another aspect is when rt rdr (say +ve angle) changes to lt rdr, the angle does not necessarily change to -ve. The rudders neutral are generally not the zero angle. So when from rt rdr you are now applying a little left rdr (say after transition) you are not applying -ve thrust, just reduced +ve angle (though rdr is left of neutral position!)