Comment # 17 on bug 1099778 from Michal Srb

I was able to reproduce it on my notebook and apparently there are no events
coming from kernel when pressing the W/S/X while holding Shift and Capslock
(tested using evtest). The notebook keyboard is internally connected with some
variant of PS/2. If I connect external USB keyboard, the key combination works
fine.

So I suspect that we are just observing a hardware limitation here. What kind
of keyboard do you use? Could you try with different one?