Pressure control solenoid

If a pcs is going bad, will the transmission slip everytime when it`s cold until it warms up? Mine will mess up about once or twice out of 10 times when the transmission is cold. I changed about half the fluid and put in a quart of Lucas Transmission Fix and it seems a little better. It doesn`t take so long to quit slipping as it did before the change. I`m going to pump out another 5 or 6 quarts and put new fluid in again.
My main question is, does it usually slip everytime when cold or just some times when the Pressure Control Solenoid is bad. I`m thinking maybe I just have old fluid.