samba - Dec 2015 - Windows File Share - Slow / Connection distrubtion

Hello,

I've installed Samba 4.3.0 and added a Server 2012 R2 as a File Share 
into the Domain. Sometimes (I can't reproduce when) the share just stops 
reacting from a specific computer, it still works for others. It looks 
like the Share is super slow and it would be a hard disk issue, but 
since it's working from other PCs I would rule that out.

I then turned up the log level to 10 and the only thing that showed up 
is that:


[2015/12/10 13:31:42.264442,  5, pid=31468, effective(0, 0), real(0, 0)] 
../auth/gensec/gensec_start.c:672(gensec_start_mech)
   Starting GENSEC mechanism schannel
[2015/12/10 13:31:42.264501, 10, pid=31468, effective(0, 0), real(0, 0)] 
../libcli/auth/schannel_state_tdb.c:166(schannel_fetch_session_key_tdb)
   schannel_fetch_session_key_tdb: Failed to find entry with key 
SECRETS/SCHANNEL/CZ-DC-01
[2015/12/10 13:31:42.264514,  3, pid=31468, effective(0, 0), real(0, 0)] 
../auth/gensec/schannel.c:563(schannel_update)
   Could not find session key for attempted schannel connection from 
CZ-DC-01: NT_STATUS_NOT_FOUND
[2015/12/10 13:31:42.264527,  4, pid=31468, effective(0, 0), real(0, 0)] 
../source4/rpc_server/dcesrv_auth.c:185(dcesrv_auth_bind_ack)
   GENSEC mech rejected the incoming authentication at bind_ack: 
NT_STATUS_NOT_FOUND
[2015/12/10 13:31:42.264935,  3, pid=31468, effective(0, 0), real(0, 0)] 
../source4/smbd/service_stream.c:66(stream_terminate_connection)
   Terminating connection - 'dcesrv: NT_STATUS_CONNECTION_DISCONNECTED'
[2015/12/10 13:31:42.264956,  3, pid=31468, effective(0, 0), real(0, 0)] 
../source4/smbd/process_single.c:114(single_terminate)
   single_terminate: reason[dcesrv: NT_STATUS_CONNECTION_DISCONNECTED]




So it looks like it can't find a session key, now I'm not sure if this 
is normal behaviour or an issue!

Could somebody chime in if this are expected log messages or if there's 
an issue / point me into the right direction to solve this?

Thanks
BR
Thomas Rosenstein