U I O keys unresponsive

The U I O keys on my keyboard have become very unreliable. I took off the top caps and cleaned out the dust, but the problem persists. Sometimes they work, sometimes they don't. Pressing all three keys in rapid succession seems to bring them back to life for a bit, but then they slip out of consciousness again…Is there anything else I can try before replacing the entire keyboard? No liquids spilled on the keyboard or anything like that.

This is on a 13" Unibody Macbook Pro Mid-2012.