Nomad 0.12.11 was released with a bug fix to avoid having new servers bootstrapping prematurely when configured with bootstrap_expect = 0 .
We shipped the fix initially in Nomad 1.0.2 and have backported it to the Nomad 0.12 line.
Links:
Changelog - https://github.com/hashicorp/nomad/blob/v0.12.11/CHANGELOG.md
Binaries - Nomad v0.12.11 Binaries