Parking lights won't go off

I have a 1997 Camry with 185K miles. Approximately every tenth time I park with the lights on the parking lights won't go off when I turn off the headlights (which I do manually, rather than just turning the engine off). The dealer relaced the headlight switch on the column, and last year I had the computer for the remote key access replaced, because sometimes the lights would go off when I just locked the car (they flashed, and stayed on). Neither solution has worked yet, and I am $600 poorer. It's hard to reproduce the problem on demand, so when I bring it in for service, the dealer can't make it happen.

Any ideas?