Hi there, I found & fixed the problem last week.
The problem is on Power door lock actuator.
Though the actuator is working by turning power door switch (switch on arm rest), but it got mechanic issue inside.
The key thing I learned from this fix is that regardless the (Front & driver side) actuator is in lock or unlock position, the small bar (which provides the power to lock/unlock your door) should be able to be freely turned (Up & down).
This special design will allow you manually lock & unlock your driver side door without power/battery.
The only problem I had is that the small bar ( Sorry! I do not know how to call it, it is just the small stick out side of actuator) was stuck when the actuator was in lock position.
Anyway, the actuator can be found in Toyota dealer by paying $230 + tax. Ridiculous!!!
From ebay, you probably be able to get it for $30~40 bucks (after market).
I went to a auto junk yard and found one by paying $17.
It is working now and I am pretty happy with the results.
After I fixed the door, I opened the bad actuator.
The interesting thing is that the actuator is wet and very very very dirty! So much dust! It was really a surprise to me!
From outside, the actuator looks clean and great! I also tested, it is indeed working when you apply power to the motor.
I was shocked that the small Japanese motor is still functionable in such a bad condition.
I may post a few pictures later on when I have a chance.
Should you have any questions about 99 Camry power door lock, I will be happy to answer. Cheers!