After weeks of racking my brain, draining and refilling, testing and adjusting everything I could think off, it's finally fixed (the light at least). I tried one more lockup solenoid. It worked.
I guess the others that I tested, seemed to be fine with a meter and the click test, but must not have been good while under pressure??
Now when the lockup occurs, I feel a shimmy from the front of the car, so I'm sure I'll need a new torque converter/tranny/? sometime soon.
Thanks to all involved for the help!