I recently changed my box to one that had been brought from Ashcroft not so many miles ago.
I know what you are saying, for what should be a box that drives like new mine sometimes takes longer to change up than I would expect.
When I first drive it I didn't fit the kickdown cable and it seemed to be fine, then after refitting the cable a drive down the road and it wouldn't change out of first, like the box I changed.
I was worried but a search led me to this post and I have downloaded and saved the link, thanks.
After adjustment it worked ok but as I say, it doesn't feel perfect all the time.
One thing I did find awkward was getting the oil level correct. When you pull out the dipstick it is always showing oil quite a way up above the level on one side. You have to keep checking the underside. I drove it home from the workshop about 3ltrs short of oil. Hopefully I have done no damage.