My 1990 Seville has a problem.

The doors will lock automatically when you put the car in grear. Then they unlock when you move the gearshift to PARK. That's wht they are SUPPOSED to do.

Some times (usually when its HOT), when I shift to PARK (engine running) the doors do NOT unlock. I press the LOCK/UNLOCK switch and NOTHING. I then have to use the manual lock lever to unlock the door. After I shut off the car and start it again everything works as it should. I will also, from time to time, hear the lock switch click while I am driving.

Any advice?

The switch on the shifter has become mis-adjusted, moved or broken. I have the same thing in my Brougham.

The switch on the shifter has become mis-adjusted, moved or broken. I have the same thing in my Brougham.

How difficult is it to get at?

Don't know mine is still broken. Is that a floor shifter? Mine is column which I imagine is pretty easy to fix.