Poor shift quality at low speeds--jerks when downshifting

What is your question?

2004 Lexus LS 430 300K miles--transmission jerks when downshifting during deceleration (approximately < 10mph). The RPMs kick up when it happens. I've heard that a software update can solve the problem. I took it to a highly recommended repair shop--replaced #2 solenoid and new Toyota transmission fluid for $700 to no avail. Still jerks; very annoying. No leaks or noises other than "thump" with it downshifts.... Any help would be appreciated.

What makes this problem better or worse?

N/A

How long has your 2004 Lexus LS430 had this problem?

About a week.