Jerking when downshifting 4th to 3rd

[evo]

I have a A8 3.0d 2008 Sport.

It's always been silky smooth but lately, the transmission, when having to downshift to 3rd (slowing down, or going up a hill) has been anything but smooth. Sometimes its a little jerking which is noticeable, but sometimes it is a bigger jerk.

The only time it is ever smooth is when I just turn the engine and off I drive with everything still cold. Eventually as it warms up, the jerk happens. There is no jerk when moving up from 2nd to 3rd or 3rd to 4th... it's ONLY when shifting down 4th to 3rd.

A lot of the time the engine decides to rev high when in 3rd without shifting up for some reason as well. Note: I never put it in S, only ever D.

What to do here??