samba - Nov 2015 - windows 10 "another process has locked a portion of the file"

I'm stumped with this.

I have a FreeBSD 10 server running samba 4.2.2 in a jail and sharing 3 
zfs filesystems. Clients pre windows 10 can map the shares and 
manipulate files fine. However when I try to map the files in windows 10 
it fails with "...another process has locked a portion of the file".

I've tried setting strict locking = no, but it seems to not help.

Meanwhile the windows 10 client can map shares from another jail on the 
same server that has a very similar samba config.

Anyone else having troubles with windows 10 clients?

Barring that anyone have tips on debugging locking?

Thanks
Russ Poyner