Nutone doorbell buzzing when Ring Pro is pressed

I’ve used the Ring Video Pro Doorbell with my Nutone doorbell for 2 years with no issues. Recently, when the ring doorbell is pressed, the Nutone will sound the first DING, make a loud buzzing sound for 10-15 seconds, then sound the second DING. The actual Ring chime sounds normal.
I recently transferred account ownership to my name, but all of the hardware was untouched (just had to repair everything in the app). Any idea why the Nutone doorbell started making this sound?

Hi @SST14. In the Ring app, with the Ring Pro selected, what do you have selected for Chime Type? This can be found by tapping Device Settings and then General Settings. If you have the wrong Chime Type selected (digital or mechanical), you could encounter the problem you are describing. Let me know if this is the case!