1993 Lincoln Continental Air ride compressor starts running

When I shutdown the engine and get out of the car, I can hear air releasing from the air struts as the car levels. However, after about 30 seconds, the air suspension compressor starts running and won't shut off unitl the front end of the car is raised way up and the front struts are solid. When I get in the car and start driving around, it only takes a few blocks and the vehicle is leveled out normally. But I stop, shut off the engine, get out of the car and about 30 seconds later the compressor starts running and won't quit unilt the front is way jacked up. If I turn off the air ride switch in the trunk, of course, the compressor stops. I can immediately turn the switch back on and the compressor will not run. I replaced the actuators on the front struts but that didn't seem to help. I've had it into a dealershp and they are baffled. They said I might neet new front level sensors but they weren't sure. But that doesn't make sense to me. If the level sensors were not working, it wouldn't level out and ride normally when the vehicle is running, either. This only happens after I shut off the engine, get out of the vehicle and shut the doors.