Just to add to Traddles' post, the problem is fairly minor, I think.
It is just that depending on how you have your controls set up, one of the two rudders does not always return fully to zero or go to hard over. But even so, the rate of turn is probably adequate (60-80 degrees/minute).
You should be able to overcome the problem by using the keys allocated to rudder 1 and rudder 2, rather than using the keys that affect both rudders.
So, unless you are experiencing problems, it is probably not worth worrying about.