[Samba] Can't write to a samba share mounted as an AD user

[pisymbol]

Full disclosure: This is an exported share on a QNAP NAS device.

[admin at outerdrive ~]# /mnt/ext/opt/samba/bin/smbstatus

Samba version 4.4.16
PID     Username     Group        Machine
Protocol Version  Encryption           Signing
----------------------------------------------------------------------------------------------------------------------------------------
14549   -1            -1                         (192.168.192.124)
SMB2_10           -                    -

Service    pid    Username    Adderess    Machine    Connected at
Encryption    Signing
QNAP need start--------------------------------------
IPC$    14549    -1    192.168.192.124        Thu Aug  2 10:25:37 AM 2018
EDT    -    -
Public    14549    -1    192.168.192.124        Thu Aug  2 10:25:37 AM 2018
EDT    -    -
QNAP need end--------------------------------------

No locked files

This is from the administrator's shell account on the QNAP device. The
share in question is 'Public'.

When I mount the share using my AD creds the mount succeeds. I can touch(1)
files and read them but for whatever reason I can't write to the share. The
ACL of the share in question looks like this:

netname: Public
    remark:    System default share
    path:    C:\share\CACHEDEV1_DATA\Public
    password:
    type:    0x0
    perms:    0
    max_uses:    -1
    num_uses:    1
revision: 0
type: 0x8004: SEC_DESC_DACL_PRESENT SEC_DESC_SELF_RELATIVE
DACL
    ACL    Num ACEs:    1    revision:    2
    ---
    ACE
        type: ACCESS ALLOWED (0) flags: 0x00
        Specific bits: 0x1ff
        Permissions: 0x1f01ff: SYNCHRONIZE_ACCESS WRITE_OWNER_ACCESS
WRITE_DAC_ACCESS READ_CONTROL_ACCESS DELETE_ACCESS
        SID: S-1-1-0

So S-1-1-0 is "everyone."

Is it because the uid/gid is "-1" in the above output causing my grief?

Thanks!

-aps