samba - Jun 2018 - Samba Share Regularly Hangs for Win 10 Client

I'm running samba 4.77 on Fedora 27 with Kernel 4.16.12.
I've got a fairly basic samba config, which I have posted below.
I use Windows 10 clients. I'm in this list because this problem only ever
seems to happen on my samba share and I'm hoping that someone will be able
to help.
>From time to time, but more often than not, Windows Explorer hangs for a
long time (10-20 minutes) when browsing my file share. Often I've right
clicked on a file and am trying to use the "Open With" menu. Before
the
sub menu even opens Explorer will hang and be non-responsive. I've even
restarted Samba during this which does not fix it. Often this can happen
immediately just after a Windows reboot. The latest episode went like
this:

11:31 PC starts up Windows 10
11:32 click the  "Open with" menu. Windows Explorer actually dies this
time and restarts itself.
11:34 Explorer very slow to give me control over any of the "View"
options
(details, icon, list etc)
11:34:45 Right click "Open with" and get the (Not Responding) problem
11:51:45 It responds

I just happened to be collecting a Tcpdump for this Windows client on port
445 for the duration of the incident.
This packet capture is available here:
 http://www.edcint.co.nz/tmp/smb.fails.tcpdump

Is anyone able to help?

-----------------smb.conf---------------------

[global]
   log file = /var/log/samba/%m.log
   writeable = yes
   server string = GW Samba Server %v
   admin users = mjurgens, vivian, jessica, jasmine, justin, julia
   workgroup = HOME
   hosts allow = 192.168.0.0/24 192.168.1.0/24 192.168.2.0/24
192.168.3.0/24 192.168.4.0/24 192.168.10.0/24
   security = user
   passdb backend = tdbsam
   unix extensions = no
   load printers = no
   wide links = yes
   kernel oplocks = yes

   # needed for DDWRT routers
   ntlm auth = yes

[shared]
        path = /export/shared
        create mask = 0775
        comment = Shared
        valid users = @family playontv