I am used to shift+shift combination for layout switching.
When I set 'shift+shift L' for switching, in unlock screen right shift does nothing, and pressing only left shift (without any other keys) changes layout.
When I set 'shift+shift R' for switching right shift starts switch layouts alone in unlock screen.
And when I set 'Alt + shift L', Alt and then Shift works OK, and Shift then Alt does not.
I am used to shift+shift combination for layout switching.
When I set 'shift+shift L' for switching, in unlock screen right shift does nothing, and pressing only left shift (without any other keys) changes layout.
When I set 'shift+shift R' for switching right shift starts switch layouts alone in unlock screen.
And when I set 'Alt + shift L', Alt and then Shift works OK, and Shift then Alt does not.
Hope this helps.