I have two Nest doorbells that I view through Google Home. Both are connected to mechanical doorbell ringers and both of those ringers are constantly in motion. See the pictures attached. The small piston-like things in them go up and down constantly. Not high enough to ring the bell (unless the actual doorbell button is pushed), but they never stop moving and are making a constant annoying up noise. Any ideas here?
That's how the Nest doorbell powers itself when you don't bring 3 wires to the doorbell location. It leaks small amounts of current through the chime. Nest thermostats do the same when you don't have a C-wire, and dimmers do the same, leaking small amounts of power through the incandescent bulb, not enough to make it get hot.
Bring 3 wires to the doorbell location.
Alternately, they make bypass capacitors which wire in parallel to the chime, and (because it's AC power) will act like a resistor "dummy load" to allow Nest's small amount of current to get by. Check with Nest for recommendations.