samba - Jun 2017 - Connection reset error when joining the domain

Hi,
 
We recently started facing this error on all new servers that need to be
integrated with AD.

Every time “net ads join -k” command is issued, following error is returned:
“Failed to join domain: failed to lookup DC info for domain X.Y.LOCAL' over
rpc: NT_STATUS_CONNECTION_RESET”. [ In the packet capture, we do see reset’s
coming from DC]
 
This is also happening on servers already connected with AD. Same error,
although since they already have established join, authentication continues to
work. Also, noticed that after doing “net ads keytab create”, keytab file is no
longer getting generated under /etc.
 
Our AD team has recently disabled SMB V1 completely on the domain controllers.
Could that be somehow causing this? I tried setting “client max protocol = SMB3”
in smb.conf but that didn’t help.
[ for " net ads keytab add" or " net ads keytab create"  it 
now says:
Ignoring unknown parameter "client max protocol"]

> OS : CentOS 6.9
> Samba: samba-3.6.23-43.el6_9.x86_64
 
How can I further troubleshoot this issue?

Many Thanks,

~ abhi