Comment 68 for bug 1245473

Maybe this is related to this bug:
https://bugzilla.gnome.org/show_bug.cgi?id=776570

I found a workaround, here: https://unix.stackexchange.com/questions/333368/gnome-3-22-disable-altshift-keyboard-layout-switching

Setting this works:
dconf write /org/gnome/desktop/input-sources/xkb-options "['grp_led:scroll']"