ring pro: mechanical chime going off randomly

I installed a ring pro a couple of days ago and everything was fine for about 24 hours until last night, the mechanical chime went off when we were sleeping.Then, within seconds, it happened again. I opened the ring app on my phone to see who was at the door and there was nobody. There was no notification from the ring app either on anyone being outside or even any motion activity. This kept happening after that.I reviewed footage going back two hours and there was no activity at the door. I came down to inspect the chime and there was a loud buzzing sound coming from it. Since it was late, I turned off the power to the chime and to the ring from the circuit breaker.Our chime is a Mechanical Nutone one with four terminals on it: COMM, TRANS, 1 NOTE, and 2 NOTE. The power pack is connected across COMM and 1 NOTE. If anyone else had the same problem, please let me know a solution if you found one.Thanks.JG