Mechanical Chime Doesn't Ring With v3 Power Kitt

I have 2 Ring doorbells and one mechanical chime. The Front is a Battery Doorbell Plus that also hardwired. The Rear is a Video Doorbell Pro 2. They are wired according to the diagram labeled "[One Ring Video Doorbell Pro/one Ring Video Doorbell/one internal doorbell chime](https://support.ring.com/hc/en-us/articles/360022454432-Wiring-Diagrams-for-Ring-Video-Doorbell-Pro-Setup )" The Power Kit is v3. My transformer reads ~21 VAC. My chime is a NuTone on the [compatibility list](https://support.ring.com/hc/en-us/articles/115003008663-Ring-Video-Doorbell-2-Chime-Kit-Compatibility-List) When the PowerKit is in circuit the Front rings fine but the Rear does not ring the chime - everything else is fine, both report Good level 1 power, camera, wifi, etc. When I remove the PowerKit the Rear will ring the chime, but the Rear reports insufficient power and the mechanical chime intermittently buzzes and rings. Is my Power Kit faulty?