[ubuntu] Ubuntu 16.04 lts hangs on shut down.

After installing Ubuntu 16.04 lts on two different PC's. I have found that they both hang on shut down!

I can restart and sleep both PC's fine, but selecting shut down hangs on the Ubuntu logo (shutting downscreen ) after a few seconds. Viewing the shut down via a terminal reports the following:

systemd-shutdown[1]: Failed to finalize DM devices, ignoring.
reboot: Power down. (Hangs here).

Restarting the PC's also say systemd-shutdown[1]: Failed to finalize DM devices, ignoring. but do restart at reboot:

I have noticed a few people with the same issue with Ubuntu 16.04 on google, but no fix! Having to press and hold the off button can't be good for the drives.

Any advice would be appreciated, thanks