can't delete or create folders in a cifs share mounted via fstab in artfull

[Dan Attwood]

I have installed ubuntu mate 17.10 Beta 2 into a brand new virtualbox machine.
I've installed cifs utils and mounted a samba shared in etc/fstab via:

//192.168.2.6/myshare /media/myshare cifs iocharset=utf8,credentials=/home/danbuntu/.smbcredentials,gid=1234 0 0

on a reboot the folder mounts correctly and I can view it's contents. However I can only read from it. I can't delete or write to it.

I recently noticed this behaviour on my desktop which has been running artfull for a few weeks.
I have also tested with vms running 16.04 and windows 10 - these work as expected and let me delete and create files so i'm pretty sure it's a bug 17.10. The 16.04 machine uses the same fstab entry

The server it's self is running 16.04 and I haven't altered any thing on apart from apt upgrades periodically.