alt + tab still works, but shift + alt + stops working. Is there something I restart to get it working again?
Do you have Shift+Alt+Tab assigned to "Switch Windows backwards" in System Settings -> Keyboard -> Windows? When I installed 0.4 Loki to Ubuntu 16.04, I had both these shortcuts disabled. I disabled Application switcher in Compiz Window settings and defined Alt+Tab and Shift+Alt+Tab shortcuts like on picture.