There is a spring loaded rod, held in place by a bushing, that centers the shift lever after you hold it over towards the driver (in between the 1st and 2nd gear gates).
The redline D4ATF causes this bushing to swell over time, which makes the centering action of the shift lever feel slow or sticky, especially when the tranny is cold.
Jeff Watson told me they fixed this problem on Bryce Danna's tranny, but the tranny had to be dropped and pulled apart. As far as I know the bushing cannot be purchased, but it can be reemed out a bit.
This is the only issue anyone has had with the D4ATF, and some people reported it even using the V160 back when there was a long thread about this on the mailing list. The symptoms were very strongly associated with the DATF though.
If your shifter is sticky first thing in the morning (hold it over towards the driver against the stop, then let it go, it should spring towards the center of the gates, do this when the car is cold and before you start it) you have the bushing problem.
Your symptoms sound like something else to me.