Keymap seems to only like some key combinations

[brontes]

So I got keymap working kind of, simply mapping "5" on my main to "3" on a clone. I can't seem to map shift-S though. When I switch 5 to shift-S it just plain does not work. I can switch back and have, say, 1 "map" to 3 and it works, then back to shift-S and no-go. This seems like odd behavior. Any ideas whats up?

Thanks.