Comment 5 for bug 1224577

I use 'Ctrl' to change my layouts and I am experiencing the same issue:

~ ➜ setxkbmap -query
rules: evdev
model: evdev
layout: us,gb
variant: ,
options: altwin:left_meta_win,grp_led:caps,grp:caps_toggle

Press [Caps Lock] to change layout:

~ ➜ setxkbmap -query
rules: evdev
model: evdev
layout: bg,gb,us
variant: phonetic,,
options: altwin:left_meta_win,grp_led:caps,grp:caps_toggle

Tweak tool configuration:

Everything 'Disabled' except
Key(s) to change layout: 'Caps Lock'
Use keyboard LED to show alternative layout: 'Caps Lock'
Alt/Win key behaviour: 'Meta is mapped to Left Win'.