Alt+Left key locks the screen

Solution 1:

This happened due to not restarting after upgrade.

I had similar problem but doesn't lock the screen rather it switches other screens in background, and it has labeled as tty1,tt2..., etc.

In my case there were 6 ttys opened and whenever I was doing alt + left arrow, it was switching to different ttys which are processes running in background and it also has login tty, kernel bootinfo tty, driver running tty.

It doesn't show only lock screen but when you switch again then you get your original chrome-screen back.

this may be the bug but after a restart, it works as we intended. hope this helps your answer.