I've had the same problem with my 2004 Camry V6.
The fix involves getting California Tech Assistance to write a program that will re-flash the control module and change the shift points on the transmission. Once written, it will come out under aegis of a technical service bulletin.
The programs have been written for Toyota Camry V6's through 2003 and Toyota Camry V4's through 2004. Same with the Sienna. Unfortunately, not enough people have complained and had cases opened for their 2004 Camry V6's to light a fire under Calif Tech (each case maps to a VIN#).
Sounds like my dealership is more on top of it than yours. They went ahead and opened a case for me (case#04340028) and for another 2004 Camry V6 owner.
It would be a real help if you could ask the service manager at your Toyota dealership to open a case for your father.
BTW, I agree with qslim that arbitration probably won't do much for you. However, you may want to file an online complaint with the NHTSA Office of Defects Investigation. There is a nice little box where you can enter the name of your dealership. After you've filed the complaint, print off a copy and show it to the service manager at the dealership, and point to the box. Together with the information that I've provided above, it should be sufficient to get a case opened. Let me know how it goes.
Plutonianfire