[Samba] Losing connection to a DC

[LOKO MESO Michel]

Hi,

I am running samba/winbind 4.2.14 on Debian 8 which is joined to an 
Active Directory and would like to know if you have any idea with my 
issue. In my case, ntlm authentification is enabled in squid (proxy).

Here is the problem that I am facing :

"wbinfo -t" takes sometimes more than 30 secondes to display the result. 
For some reason, the server loses it's connection to the domain controller.

I found the following line in /var/log/samba/log.wb-MY contains :

[2019/02/13 15:02:19.850547,  0] 
../source3/winbindd/winbindd_cm.c:918(cm_prepare_connection)
   cm_prepare_connection: mutex grab failed for my.domain
[2019/02/13 15:03:09.928405,  0] 
../source3/lib/util_tdb.c:493(tdb_chainlock_with_timeout_internal)
   tdb_chainlock_with_timeout_internal: alarm (40) timed out for key 
my.domain in tdb /var/run/samba/mutex.tdb
[2019/02/13 15:03:09.928477,  0] 
../source3/winbindd/winbindd_cm.c:918(cm_prepare_connection)
   cm_prepare_connection: mutex grab failed for my.domain

What happens when /var/run/samba/mutex.tdb is locked with a timeout ? 
Does this mean that users authentication stops working and that the 
winbind is unable to comunicate with the DC ?

Thanks,

Michel