[Samba] samba 4 ad and issues users logon

[Trenta sis]

hi,

We recently have migrated a samba 3 nt domain to samba 4 AD, v4.4.5, and
results are ok, but we detectes one issue with users logon, in random
situations our users are reporting that they receuve an error message that
password, is incorrect, and in this situations we can confirm that
credentials are ok. After 1 or 2 minutes they can logon without problems.
I have searched errors in samba logs, linux.. and any error is found...
Anybody can help to found where is the problem?

Thanks