You should not "add" a power supply to keep it on during a power outage. You should also not remove a relay and replace it with jumpers. Both of those things can be very dangerous to the next person to work on the elevator or even you if there's an emergency and you forget. Im not familiar with garaventa but other residential elevators but I have worked on other residential elevators and if the power supply is weak or damaged you can get similar issues. Start with replacing the power supply. Other residential elevators use power supplies that take 240vac and turn it to 24vdc so you could go that route. You could also check your power supply output (the DC side) on a with your meter. You should have less then 10 milli volts of ac ripple
