Comment # 15 on bug 1099778 from Michal Srb

I can reproduce. With

  setxkbmap "us,cz(ucw)" -option grp:caps_switch

Capslock+Shift+w = nothing
Capslock+Shift+s = nothing

By the way, also:
Capslock+Shift+x = nothing (but maybe that is expected)

I tested in Leap 15 in KDE and in Gnome.

Xev shows that no event is delivered at all when the W/S/X button is pressed.
So it seems that it is not a problem of the mapping, but something prevented
the event from being sent. I'll try to debug where it is lost.