[Samba] samba 3.6 client signing

[Reardon, Timothy CONTRACTOR @ ERD-NH]

Hi
We have 2 servers running samba
1 is linux 7 /samba 4.2.3
1 is linux 6 /samba 3.6.23-25.0.1

Both are joined to a Windows Domain
Both use ADS for security (we use CAC on the client)

Recently users of the samba 3.6 shares have been having trouble connecting

The issue seems to be theclient  registry setting :
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\lanmanworkstation\parameters\EnableSecuritySignature

Users cant connect to the 3.6 shares with it enabled
They can connect to the 4.2.3 shares 

We have tried server side smb.conf settings but no luck
They can only connect when  the client registry key is disabled
(and this violates a STIG)

Anyone seen this?

Thoughts?
Thx
tim

Tim Reardon - GCED/GCFA/GCIH/GISP/GSEC 
RS/GIS CX Systems Administrator
ERDC-CRREL
Hanover,NH 03755
603-646-4332
Timothy.P.Reardon at usace.army.mil