phabulous: Transient slack auth errors

I followed the Getting Started guide and run into errors that indicate my slack auth is not working. I execute ./phabulous serve in debug mode and see a lot of log lines that appear to be data from slack which includes channel and user data, but after a few seconds the logs indicate there was a slack auth issue.

phabulous joins configured channel with message: Hi! Phabulous v3 reporting for duty!, then goes offline.

Logs:

time="2018-01-02T19:01:53Z" level=debug msg="Logger is debug level."
time="2018-01-02T19:01:53Z" level=debug msg="Booted upper layer."
time="2018-01-02T19:01:53Z" level=info msg="Starting RTM handler..."
time="2018-01-02T19:01:53Z" level=info msg="Starting up the API server..."
[GIN-debug] [WARNING] Running in "debug" mode. Switch to "release" mode in production.
 - using env:   export GIN_MODE=release
 - using code:  gin.SetMode(gin.ReleaseMode)

[GIN-debug] GET   /                         --> github.com/etcinit/phabulous/app/controllers.(*FrontController).(github.com/etcinit/phabulous/app/controllers.getIndex)-fm (3 handlers)
[GIN-debug] GET   /healthcheck              --> github.com/etcinit/phabulous/app/controllers.(*FrontController).(github.com/etcinit/phabulous/app/controllers.getHealthCheck)-fm (3 handlers)
[GIN-debug] POST  /v1/feed/receive          --> github.com/etcinit/phabulous/app/controllers.(*FeedController).(github.com/etcinit/phabulous/app/controllers.postReceive)-fm (3 handlers)
time="2018-01-02T19:01:53Z" level=debug msg="API Server Hostname: :8085"
[GIN-debug] Listening and serving HTTP on :8085
time="2018-01-02T19:01:53Z" level=debug msg="RTM Event received."
time="2018-01-02T19:01:53Z" level=info msg="Attempting to connect to Slack (Attempt #1)"
time="2018-01-02T19:01:54Z" level=debug msg="RTM Event received."
(big user data blob log lines)
time="2018-01-02T19:01:54Z" level=debug msg="Connection counter: 1"
time="2018-01-02T19:01:54Z" level=info msg="Bot Slack ID:  U8MAN9WG5"
time="2018-01-02T19:01:54Z" level=debug msg="RTM Event received."
time="2018-01-02T19:01:54Z" level=debug msg="RTM Event received."
time="2018-01-02T19:01:54Z" level=debug msg="RTM Event received."
time="2018-01-02T19:01:54Z" level=info msg="Attempting to connect to Slack (Attempt #1)"
time="2018-01-02T19:01:54Z" level=debug msg="RTM Event received."
time="2018-01-02T19:01:54Z" level=error msg="Unable to connect/authenticate with Slack. Check the bot's credentials."
time="2018-01-02T19:01:54Z" level=debug msg="RTM Event received."
time="2018-01-02T19:01:54Z" level=info msg="Attempting to connect to Slack (Attempt #2)"
time="2018-01-02T19:01:54Z" level=debug msg="RTM Event received."
...