I've got eOS (0.4.1 Loki) on my Desktop and Laptop at this time. On my Laptop when I leave it open for some time it goes to a stage like sleep, only I can't recover it. I am seeing a white underscore on the top right corner of the screen.
I've tried all kind of schortcuts but nothing works. I can recover only if I hard close the system from the power button or sometimes if i press it once and go to sleep. Then I re open it and everything works fine.