[Samba] User accounts being blocked

[Ricardo Pardim Claus]

Dear, 
I've been noticing that constantly, some user accounts has been repeatedly blocked. 
We use DC Samba 4.4.5. 

Here we have a blocking policy, if the wrong password is entered more than 5 times. But most users say they do not screwed up the password. They perform the log at the beginning of working hours. After a while, they block the session and when they try to log on again, the message of blocked account. 

The same thing happened with two users who work with me. And today I experienced the problem, rebooted my desktop when I perform logon, I received the message that the account was blocked. 
We perform other test. We managed to block an account with only 3 attempts to wrong password. 

Someone can tell me where I can check the Samba logs the account lockout reason? 

We performed a search on all machines and servers, the search for malware, but nothing was found. 

Thank you!