Ramon Davila is one name in a growing list. He’s among the nearly two dozen federal background check investigators to face criminal charges in recent years for falsifying his work on investigations performed on contractors and employees seeking government clearances. But more than year after charging Davila, the Justice Department only just learned that he had a troubling past that went unnoticed during his own background investigation. It turns out, officials at another federal law enforcement agency decided nearly a decade ago to keep out of his personnel folder serious misconduct findings against Davila stemming from his years as a…