Following this update, one of my client machines, running Rune, was no longer able to access my music library share. The Samba log showed:
[2017/05/26 13:06:58.425671, 0] ../source3/auth/auth_domain.c:225(domain_client_validate)
domain_client_validate: unable to validate password for user eddie in domain DISCWORLD to Domain controller NSDC-NETHSERVER.BOGOLINUX.NET. Error was NT_STATUS_WRONG_PASSWORD.
Turns out that Rune was forcing the "sec=ntlm" parameter on the mount, which I'm guessing isn't usable after this update. Although I haven't been able to find anything that documents this.