[Samba] Fileshare - how to enable Modify permission for an rwx-enabled file

[Mgr. Peter Tuharsky]

Hi,

I'm searching the web for a while but cannot find an answer to this,
even on Samba wiki, so please, does somebody have a clue, how to enable
MODIFY access permission for a file that is located on Samba share?

The fileserver is Samba, member of AD domain, local filesystem ext4,
basic ACLs. The file has properly set rwx for users and groups needed,
both for a file and for parent directory. However, for Windows 10 /
Windows 2016, the file Properties - Security tab reports only Read &
Execute, Read, Write, Special permissions rights for the said
users/groups. The Modify permission is NOT SET. In effect, when the user
opens the file in Office app, he gets "file is read only" warning. OTOH,
user can create new files in directory.

We haven't had such problem with samba 4.2 fileserver, member of NT4 domain.

Has the ACL translation model changed since? Or what might be a culprit?
What should I do to make samba enable Modify permission for RWX-enabled
files?