Transmission Mechanic?

[Mike W]

I have owned a '07 ES350 since May '06. The transmission once in a while exhibits what is called here flare. I have researched all past posts on this forum. I also went on Lexus and pulled up their three versions of their TSIB's. The flare as it is called is really the clucth packs slipping slightly on shifting. Having been a mechanic for a very long time I'm looking any specific knowledge anyone has as to the true cause of the problem. I have read the assumptions and conclusions but am interested if anyone really knows the problem and solution. My dealer has been most cooperative and although the times they have driven it they have not been able to duplicate the problem they went ahead and reflashed the software. On the way home from the dealer it occurred again. 2000 RPM light throttle at 40 MPH. 200 RPM increase just before shift. I can correct the occurrence but not the probelm by driving it (wife's car) like I drive my BMW but shouldn't have to.