As this issue is really difficult to reproduce (I've only seen it once here), could you please attach some logs from right when/after it happens?
We'd be interested in /var/log/lightdm/lightdm.log, /var/log/lightdm/x-0-greeter.log, /var/log/lightdm/x-1-greeter.log
You'll need root access to grab these logs.
Please check whether there is any sensitive information in these logs that you don't want to publish before uploading them!
As this issue is really difficult to reproduce (I've only seen it once here), could you please attach some logs from right when/after it happens?
We'd be interested in /var/log/ lightdm/ lightdm. log, /var/log/ lightdm/ x-0-greeter. log, /var/log/ lightdm/ x-1-greeter. log
You'll need root access to grab these logs.
Please check whether there is any sensitive information in these logs that you don't want to publish before uploading them!