If it is not the duovalve, it is one of these things:
1) The climate control module's PWM output to the drivers side of the duovalve is failing - probably a bad pass transistor on the main board. Replacing the module will fix that.
2) Corrosion on the pin at the duovalve for the driver's side coil. (I have not seen corrosion do this, but it sure can do it. The fact you rebuilt the valve tells me you have already disconnected and reconnected, which often cleans enough corrosion to clear such an issue for some time.)
3) Corrosion or bad crimp on a pin in one of the connectors between the duovalve and the climate module. (I found this ONE time, back in about 2017 in an SRT Roadster.)
4) Failing battery power to the duovalve (but this would cause BOTH sides to go hot).