[ubuntu] 16.0.4 not shutting down - just hangs forever

Acer laptop ha been ruing 14.0.4 for years. Decided to switch up to 16 and in a moment of haste clicked "Erase and install..." so no 14 to fall back to. My fault I know, but 16 is not shutting down.

It seems to work fine for everything, but when I click the gear in top right then "Shut down" and finally click the right-side button to really shut down, it shows a "DOS-like" display scrolling past for about 5 seconds the I get the purple "Ubuntu" with the five dots beneath it.

The dots roll through orange and white as normal, but it just sits there. I left it ruing last night for two hours and same so pulled the plug.

This moing tried again and it started up and worked fine, used "sudo apt-get update" etc and all good. But, shut-down is not working again and I am back at the purple screen and rolling dots forever.

The 14LTS used to shut down fine.

Thoughts? Fixes?