Authentication Failure Switch to greeter

I'm experiencing a very annoying problem on Ubuntu 18.04.

Whenever my laptop resumes after being suspended I'm completely unable to login and get the error;

Authentication Failure Switch to greeter

The issue is well described here, although it seems no one has found a solution to it.

https://bugs.launchpad.net/ubuntu/+source/unity/+bug/1733557

Is there any way to stop this from happening?

Update:

To anyone who comes across this, the shortcut to get to the greeter without having to reboot is Ctrl-Alt-F1.

Also if anyone of the people who voted to close this question had actually read the bug report above they'd see that users still report the same issue after upgrading to 18.04.

As per Michael Durrant's comment above and this post:

$ sudo apt install --reinstall lightdm
$ sudo service lightdm restart

Note: Running this command will log you out of your system. So, make sure to save your work before that.

I resolved the issue by a simple restart.