Odd issue
If the passenger side switch will lock both doors, then the mechanicals in the door and the actuator are fine.
I would start by unplugging the switch panels from both sides of the car. Then plug the passenger side switch into the driver's door and try it. If it works, then you just have a bad switch in your driver's side panel. (This happens from time to time and I've had to replace several window switches over the years.)
If you have a bad switch, be careful!!! The panel gets brittle as it gets old and if you stretch it to far prying the old switch out, it could crack.
Do the lights come on/go off properly when the door opens? That should tell you if the wiring to the door switch is working.
For the locking issue, I think you are down to tracing the wires from the lock switch in the door to the BCM to find out where the issue is. If you log on to Autozone.com and go to the repair section, they have all the official GM schematics.
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... One thing to look at might be doing the BCM solder fix again and targeting specific connections. Sometimes it takes two passes and/or additional solder needs to be added.
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