It's a problem with keyboard ghosting. That's the problem with chording keys like this, once you're hitting >= 3 keys, you'll find some just won't work.
After 5 minutes: I can not get G either!!!
Paul, can you change time intervals to to catch less accurate chors?
I have it set to 125ms. I bumped it to 200 and it felt really unresponsive.
When in doubt, make a configuration option right? ;)