Welcome to the Forum, @bradsfish, and thanks for sharing your experience! 
These things are so goofy that I’m not sure what to make of the way they’re supposed to work anymore. I’d previously read about reversing the terminal connections for the Chime Controller’s red and white wires, and I was aware of the alternate wiring instructions, but my doorbell was working fine with the mechanical chime for months…until it wasn’t.
When restarting no longer resolved the issue, I learned that holding the button in for 1-2 seconds worked…sometimes, but I can’t expect everyone who attempts to ring the doorbell to know that. I also had limited success by switching the Doorbell Chime Type to Digital and changing the Ring tone length parameter…until that stopped working, too.
A couple of days ago I tried the alternate wiring instructions, so now the Chime Controller’s white wire isn’t connected to anything, and the mechanical chime works once again…but for how long?
Your information just adds to my confusion, but I reckon it’s good to know because it might be one more variation to try if I have a future failure.
How did you determine that the wires were reversed at your chime?
Edit: Okay, so I still don’t know how @bradsfish made this determination, but trying to assist with a doorbell chime issue in another topic led me to do some more thinking, and I came up with my own solution, which resulted in rewiring my own chime box, because I was able to determine that the red wires in my chime box were on the wrong FRONT and TRANS terminals before I ever began my initial installation.