This is pretty reproducible. @bradrydzewski have you been able to reproduce it? I have been able to run the drone container locally with ngrok and found the exact same problem.
Sorry, I am unable to reproduce. I just ran a test a few minutes ago and can confirm Gogs (0.11.79.1211) was able to process the webhook without issue, and successfully triggered a build. There are also a number of individuals in our gitter running rc.2 with Gogs and Gitea without issue. So it would appear to be something related to your configuration or environment …
@arca1n I noticed that you had DRONE_TLS_AUTOCERT=true even through Drone is behind a reverse proxy. This field should be disabled and could impact inbound http traffic. I recommend disabling.