I just do not like the aftermarket style modulator, A pet peeve of mine. You will not see them for long on any of my cars. When that plug is unplugged, it shifts fine. When I plugged it in it did not want to shift. I did not get to drive it far because of the weather.
I think your downshift/kickdown solenoid is getting power all the time, when the terminal is connected. Meter or test light and see if that terminal (end of the wire) is always energized with the key on/engine running (while disconnected).
Ok, I checked the switches and they seem to work as they should. I adjusted them and it seems to work so I will try to get a chance to road test it and report back.