I am currently going back and forth via email with August support for the same problem. As I'm sure you've read, there was a bad firmware update three to four years ago and in my case a downgrade to 1.59.0-1.8.15 solved the issue. My lock worked perfectly after that both on a C3 with S0 security and a C7 with S2 security.
Fast forward to two weeks ago- I wanted to recalibrate the DoorSense, and 1.59.0-2.0.4 was pushed to my lock (August promised I'd get no futher updates). Six hours later, the lock stopped responding to Z-wave commands unless the August app was also connected via bluetooth. I've requested another downgrade and am waiting for a response.
Unless I get an adequate response from them soon, I am probably going to try a Danalock v3 with either zigbee or Z-wave.
I'll let you know what August has to say.
