Hello, I have had this problem from new and my gearbox, has been adjusted twice, don't know how and Lexus have made modifications to the selectors twice. I'm now on about 33,000 miles and it probably won't get any better. It is better than it was but not good. 1st to 2nd is the worst and at times is very stiff and clunks in. I find that if I change gear slowly then it is mpostly better.
I have repeatedly had a go at Lexus for not offering an auto option on the deisel and about the quality of the gearbox. To be honest, this is the single thing that may stop me buying another Lexus.
My partner drives a new Seat and her gear change is fantastically smooth, as I constantly remind my dealer, so why can't the Lexus one perform as well.