One more for the mix:
I experience this behavior in most cases when light-locker kicks in as screen saver. Closing the lid or suspending never triggers this. i965 driver on Sandybridge CPU. Ctrl-Alt-F6-F7 brings me to a screen-is-locked display, and after some seconds, to the actual login prompt. Bug appeared after upgrading from stretch a few months ago. Debian/Buster, light-locker 1.8.0-3. I tried using the keys to change screen brightness, no effect.
