https://forum.manjaro.org/t/keyboard-layout-change-on-hotkeys-press-instead-of-release/
I have exactly the same problem, but that question was closed without any answers 
When I set Alt+Shift or Ctrl+Shift to change my keyboard layout, all hotkeys including Alt+Shift/Ctrl+Shift stop working.
.bump.
Well I would expect Alt + Shift to match before Alt + Shift + key.
Why don’t you try something like Alt + Space for changing keyboard layouts, and leave the more common modifier combos for hotkeys?
Because I want to have everything!
Alt+Shift for changing layouts and Alt+Shift for combos at the same time !1!!