I pulled the schematics for the circuits you're having issues with and both switches are in the same unit and share a ground wire. If the switch is a known good part then you have a short to ground in the circuit. I would pull out the switch and inspect the connector and wires for any loose or exposed wires.
I would strongly suggest having a competent tech do the work for you unless you have a good understanding of electrical systems. Did you replace the switch yourself or did a tech do it? The switch would have been my first guess and they weren't necessarily wrong to replace it. EDIT: I originally said they should be able to prove that the switch was faulty but because it's an intermittent issue it would be very difficult to prove. Still, you may want to talk to them about reimbursing any parts and labor for replacing the switch. Also, you should not pay them again for diagnosis as they did not diagnose it right the first time.
I read your other thread where you said you were having transmission problems. This particular switch is located directly above the transmission, and any kind of funky wiring where B+ is becoming grounded to the transmission case could definitely cause faults with the transmission module. I would definitely fix the wiring before you consider anytransmission work.