[Samba] problems accessing shares with force group

[Piviul]

I have a strange behaviour from samba 4.5.16: I can't access to a share 
if I set the force group parameters. For example if I set in smb.conf:

> [test]
>    comment = test force group share
>    browseable = no
>    path = /home/test_share
>    force group = "@MYDOMAIN\Domain Group"
>    write list = "@MYDOMAIN\Domain Group"
>
when I access to the share I get an error but if I comment the force 
group directive I have no problem accessing the share.

I wrong something?

Piviul