[Samba] domain users issue

[Trenta sis]

Hi,

Using a samba 4, and having users configured as primary group domain
users (513) we detected that then if you execute net group /domain
"Domain Users" then user is not showed in as member of domain users,
if you remove from primary group and assign another group then with
net group /domain "Domain Users" you can list this user as member.

This generates that for example permissions to ahres assigned to
doamin users are not working

Anybody can give some information where is the issue, reproduced with
samba 4.4.5 and 4.4.16

thanks