[Samba] no connections yet target is busy, can't unmount

[Zalth]

New to samba. Win7 machine cleanly shut down on home network, umount still reports "target is busy". What needs tweaking?

With the Win7 machine shutdown, umount succeeds (seemingly only) after restarting smbd, for example: systemctl restart smbd

Samba version 4.5.16-Debian

Samba is installed standalone, (from /etc/samba/smb.conf:
server role = standalone server )