Doorbell Ringing at night -- dropping voltage

I've got two Video Doorbell Pro units hooked up for front and back. I'm using the Ring transformer and the existing wiring and mechanical doorbell. The only problem I have is that the mechanical doorbell will ring at night, followed a an electrical buzzing noise, then ring again to the point that I have to shut down the breaker. The weird thing is that it doesn't do this every night and it doesn't appear to be weather/temperature related. When it does happen, I check device health and it shows poor voltage for each device. Any thoughts? I have purchased a new transformer that is 24v and 40va, but I'm not sure that will solve the problem.