Can't save files created by others in samba shares

Question

My system is FreeBSD 13.2, samba 4.16. I've set up some samba shares and added users and groups to access these shares. Now from Windows 10 the users can navigate the samba shares, can create and delete files and folders on it. The problem I have is user_b can't save files created by user_a when he's done modifications, even user_a and user_b are in the same group. What am I doing wrong? Here is /usr/local/etc/smb4.conf:

# Global parameters
[global]
        netbios name = JFSVR
        passdb backend = tdbsam
        realm = WKGRP.IO
        workgroup = WKGRP
        max connections = 30
        vfs objects = dfs_samba4 zfsacl
        server role = standalone server
        security = user
        ntlm auth = yes
        local master = yes
        log level = 3
        max log size = 5000
        log file = /var/log/samba4/%m
        os level = 255
        hosts allow = 127.0.0.1 192.168.0.0/16
        dns forwarder = no
        dns proxy = no
        interfaces = bce0
        bind interfaces only = yes
        socket options = TCP_NODELAY
[store1]
        path = /jails/samba/store1        # jail is not configured, "jails" is just the name, samba is not running inside jail.
        valid users = @mgmt, @eng, @mfg, @sales, @qual, @purch, @hr, @fina, @oper
        write list = @eng, @mfg, @sales, @qual, @purch
        browseable = yes
        writeable  = yes
        guest ok = no
        public = no
        create mask = 0777
        force create mode = 0777
        directory mask = 0777
        force directory mode = 0777
        inherit acls = no
        inherit owner = no
        inherit permissions = yes

I tried to play with acl and see if it helps, but no success. For example,

# ll
drwxrwxrwx   2 user_a  eng        3B Jun 12 14:11 test/
# cd test;ll
-rwxrwxrwx  1 user_a eng   171B Jun 12 14:40 test.txt*

# setfacl -m u:user_b:rwxp::allow,g:eng:rwxp::allow test.txt
# getfacl test.txt
# file: test.txt
# owner: user_a
# group: eng
       user:user_b:rwxp----------:-------:allow
         group:eng:rwxp----------:-------:allow
            owner@:rwxp--aARWcCos:-------:allow
            group@:rwxp--a-R-c--s:-------:allow
         everyone@:rwxp--a-R-c--s:-------:allow

Now user_b can open file test.txt, but can't make changes then save it from Win10. I should point out that user_b can login to FBSD system, and make changes to test.txt and save it just fine.

Helps are highly appreciated.

Searched the site to find solutions, tried tips mentioned in some posts, but they didn't solve my problem, I still can't save files created by other users, from Windows 10.